The days of the week: gods, planets and lost sounds

The English week is a translation. The Romans named their seven days after the seven heavenly bodies they could see moving across the sky — the sun, the moon, and the five planets known then, each a god: Mars, Mercury, Jupiter, Venus and Saturn. That is why French still has mardi (Mars), mercredi (Mercury), jeudi (Jupiter) and vendredi (Venus).

Germanic peoples adopted the Roman week while they lived along the empire's borders, and they translated it rather than borrowing it. The sun and moon were easy: Sunday and Monday. For the gods, they looked for their own equivalent of each Roman one: Mars became Tiw, Mercury became Woden, Jupiter became Thunor (Thor) and Venus became Frig. Only Saturn had no match, so Saturday kept the Roman god.

Over a thousand years of sound change, most of these names stopped sounding the way they are spelled. Each day below has the full story on its own page.