Frigg, Freyja, Venus and the Naming of Friday

Dies Veneris, Venus's day, became Frigg's day among the Germanic peoples, preserved in English as Friday, matching the Roman goddess of love and beauty to the Norse goddess of marriage and the hearth under interpretatio germanica. The identification is genuinely debated in scholarship: some sources hold the day was originally named for Freyja, a separate Norse goddess more directly associated with love, beauty and desire and therefore a closer match to Venus's own character, and argue that Frigg and Freyja had become difficult to fully distinguish by the time Old English and Old Norse sources describing the day name were written down.

The Romance languages kept the Latin planet directly, as with the rest of the midweek: venerdi in Italian and vendredi in French both preserve Venus by name. Whichever Germanic goddess actually stood behind the English name, the underlying logic follows the same pattern as Tuesday, Wednesday and Thursday, a Roman planetary deity matched to the Germanic figure judged closest to her in character and function.

Sources Norse Mythology: A Guide to the Gods, Heroes, Rituals, and BeliefsJohn Lindow with Deutsche MythologieJacob Grimm