Were the Days of the Week Really Named After Norse Gods? (It’s More Complicated Than That)

Here’s a piece of Norse mythology trivia that circulates constantly online, in classrooms, and in the kind of books you find in the mythology section of a large chain bookstore: Tuesday is named after Tyr. Wednesday is named after Odin. Thursday is named after Thor. Friday is named after Freya/Frigg.

It’s tidy. It’s memorable. It’s the kind of thing that makes people feel connected to this ancient tradition every time they glance at a calendar.

It’s also, as with so many “facts” about Norse mythology, significantly more complicated than the version that usually gets shared, and the actual story is far more interesting.

As someone who has spent nearly two decades researching Norse mythology, history, and culture to build the world of Leifthasir’s Saga, I have a lot of feelings about how often the interesting version of a story gets swapped out for a simpler one that sounds better in a listicle. So let’s fix this one properly.

First: The Days of the Week Didn’t Come From Norse Mythology

They came from Babylonian astrology, transmitted through the Roman Empire, calqued into Germanic languages, and only eventually connected to the Norse gods you’re thinking of, but not in the way you were probably told.

Here’s the chain:

The seven-day week originated in ancient Mesopotamia. Babylonian astrologers divided the lunar cycle into four phases and assigned each day to one of the seven visible celestial bodies they could observe: the Sun, the Moon, Mars, Mercury, Jupiter, Venus, and Saturn. This system was absorbed into Hellenistic astrology after Alexander the Great’s conquests spread Greek culture across the ancient world. The Romans picked it up, organized it into a formal system, and by the 1st through 3rd centuries CE, the Roman Empire had replaced its own eight-day market cycle with this Hellenistic seven-day week.

The Latin names: Dies Solis (Day of the Sun), Dies Lunae (Day of the Moon), Dies Martis (Day of Mars), Dies Mercurii (Day of Mercury), Dies Iovis (Day of Jupiter), Dies Veneris (Day of Venus), Dies Saturni (Day of Saturn).

Germanic peoples living along the Roman frontier (the Rhine and Danube border regions) encountered this calendar through contact with Roman soldiers, traders, and administrators. And instead of just borrowing the Latin names directly, they did something linguistically fascinating: they translated the function of each Roman deity into its closest Germanic equivalent, then named the day after that Germanic god.

This process is called interpretatio germanica, which is literally the Germanic interpretation of Roman religious concepts. It’s the same instinct that led Roman observers like Tacitus to describe the Germanic chief god Wōden as their version of Mercury: not because they were identical, but because they shared enough functional overlap to map onto each other meaningfully.

The result is what we now call the English days of the week.

The Mapping: Who Got Substituted for Whom

The pairings are more thoughtful than you might expect.

Tuesday comes from Tīw (Old English), the Anglo-Saxon equivalent of the Norse Týr, a god associated with warfare, single combat, solemn oaths, and the legal assembly called the þing (Thing). He replaced Mars, the Roman god of war. The functional overlap is direct and logical.

Wednesday is Wōden’s day, the Anglo-Saxon form of what you know as Odin. And this is the one that surprises people, because Wōden replaced Mercury, not Jupiter. Why? Because Roman observers consistently noted that Wōden and Mercury shared a set of roles that Jupiter didn’t: both were gods of travelers and wind, both served as psychopomps who guided souls to the underworld, both were patrons of eloquence, trickery, and esoteric knowledge. The obvious choice for the king of the gods might have been Jupiter, but the functional match was Mercury.

Thursday is Thunor’s day, the Anglo-Saxon equivalent of Thor. He replaced Jupiter, the Roman god of thunder, lightning, and the upper atmosphere. This one is the most direct mapping in the whole set: atmospheric weapon, thunderstorms, cosmic protector. Thor and Jupiter are playing the same role in their respective mythologies.*

Friday is where things get genuinely interesting, and where the most common misconception lives.

*It is important to note that Thor isn’t the god of storms and thunder, but is associated with these things because of his rage, and the sounds Mjolnir, his hammer, makes when he strikes his enemies. We relate to Thor as the god of thunder because the Romans tied him to Thunor.

Friday Is Not Freya’s Day

This is the one I find myself correcting most often, because it has become so thoroughly embedded in popular Norse mythology content.

Friday replaced Dies Veneris, which was Venus’s day. And Venus was mapped not to Freya, but to Frigg: the wife of Odin, queen of the Aesir, a goddess associated with marital love, household harmony, and prophetic wisdom. The Old English form is Frīgedæg, derived from Frīg, which is the Old English name for Frigg.

Freya, the Vanir goddess usually associated with magic, desire, and erotic love, is a specifically North Germanic figure. Her name appears in Old Norse but has no equivalent in early West Germanic dialects. She simply wasn’t part of the Anglo-Saxon pantheon in the way Frigg was. By the time the Roman planetary week was being translated into Germanic languages, the name assigned to Venus’s day was Frijjō—Frigg—not Freya.

Are Frigg and Freya possibly the same figure at some deep Proto-Germanic root level? Some scholars think so.** But that academic debate doesn’t change what the philological record shows: Frīgedæg is Frigg’s day, not Freya’s, and the popular version has the wrong goddess.

**In this author’s humble opinion, no, Frigg and Freya are not the same person. I will always argue that Freya and Frigg occupy different roles in Norse myth because they occupy different roles that women play, or different views on femininity as the Norse saw it. To reduce Freya and Frigg, and even Gullveig, into one person removes the rich tapestry of ancient Nordic womanhood into one binary.

Here’s the Part That Really Changes the Story

So far, you might be thinking: okay, so it’s Germanic gods, not specifically Norse gods. But here is the fact that most popular retellings skip entirely:

The English days of the week were not borrowed from Norse mythology. They predate Viking contact with England.

The Anglo-Saxons settled Britain in the fifth and sixth centuries CE; roughly two hundred to three hundred years before the Viking Age began in the late 700s. Old English was already forming. The weekday names were being established. By the time Norse-speaking Scandinavians started arriving on English shores, the Old English calendar was already using Tīwesdæg, Wōdnesdæg, Þūnresdæg, and Frīgedæg.

Old English is West Germanic. Old Norse is North Germanic. They’re cousins, not parent and child, two branches of the same family tree that had been developing independently for centuries before any Viking ever set foot in Northumbria. The gods they share (Tīw/Týr, Wōden/Óðinn, Þunor/Þórr, Frīg/Frigg) descend from the same Proto-Germanic source, but they are not the same gods. They evolved separately.

In fact, the influence runs the other direction from what most people assume: North Germanic languages actually borrowed the seven-day week framework from West Germanic dialects, not the other way around. Old Norse forms like Frjádagr show phonological markers indicating they were adapted from West Germanic prototypes, Old Frisian Frīadei or Old High German Frîatac, rather than created natively from Old Norse. A fully native Old Norse construction would have looked more like Friggjardagr.

What the Church Did to All of This

Once Christianity spread across Europe, the fact that people were invoking the names of pagan deities every time they mentioned what day it was became something of a theological inconvenience. Church authorities pushed back in several regions with varying degrees of success.

In Portugal, they succeeded completely. In the sixth century CE, Saint Martin of Braga wrote a treatise against naming days after pagan gods and introduced a liturgical system of ordinal numbers instead. Modern Portuguese still reflects this: Segunda-feira (Monday/Second Market Day), Terça-feira (Tuesday/Third), Quarta-feira (Wednesday/Fourth), and so on. Portugal is essentially unique among major Romance languages in having completely erased the Roman planetary gods from its calendar.

Iceland, interestingly, did something similar but for Norse gods specifically. In the twelfth century, Bishop Jón Ögmundarson banned the use of Týsdagr, Óðinsdagr, Þórsdagr, and Frjádagr, the days named after the old gods, and replaced them with liturgical and positional terms. Modern Icelandic uses Þriðjudagur (Third Day/Tuesday), Miðvikudagur (Midweek Day/Wednesday), Fimmtudagur (Fifth Day/Thursday), and Föstudagur (Fasting Day/Friday). This makes Icelandic, ironically, one of the languages most associated with Norse mythology, one of the few Germanic languages with no pagan god names in its weekly calendar.

Germany partially succeeded: monastic reforms replaced Wōden’s day with Mittwoch (“midweek”), which survives in modern German. English, by contrast, preserved the old system almost entirely intact.

Saturday is its own footnote in this story. It’s the one day where interpretatio germanica broke down; nobody could find a clean Germanic equivalent for Saturn, whose mythological role was strange enough (agriculture, a golden age, time itself, the defeat of earlier titans) that the Germanic translators just borrowed the Latin name directly rather than substitute a native deity. Old Norse, however, rejected this and went its own way: Laugardagr, meaning “bath day”, a reference to the weekly bathing ritual performed before Sunday. This survives in modern Swedish (Lördag), Danish and Norwegian (Lørdag), and Icelandic (Laugardagur).

Why This Matters (And Why I Care About It)

I write Viking dark fantasy. My entire creative practice is built on the premise that the more accurate your understanding of the source material, the richer the fiction you can build from it. Every time a simplified version of Norse mythology gets repeated as fact, it makes that source material a little shallower, and a little less interesting for everyone who encounters it.

The real story of the weekday names is not “the Norse named the days after their gods.” It’s a 3,000-year transmission chain from Babylonian astral observation through Hellenistic astronomy through Roman administrative calendar reform through early Germanic cultural contact and translation into the working language of a people who would eventually become the English-speaking world. That is extraordinary. Every time you say Tuesday, you are speaking a word that contains the functional echo of Mesopotamian stargazers, Roman legionnaires on a Rhine frontier, and West Germanic translators who looked at Mars and saw a god they knew better by another name.

That is the kind of history that earns its complexity. And it’s the kind of history that, when you actually understand it, makes the mythology it’s rooted in feel alive in a way that the simplified version never quite achieves.

A Quick Reference: What Actually Happened to Each Day

If this kind of deep dive into what Norse mythology actually was, as opposed to what we’ve been told it was, is your thing, I write about it regularly here on the blog. The same research that informs posts like this is the research that goes into every book in the Leifthasir’s Saga series, where I try to build a world grounded in what the Eddas, the sagas, and the archaeology actually tell us.

A Tale of Scorched Ash and Elm and the companion novellas are available in my shop.