The ancient Babylonians, then the Romans, named the days of the week after planets and other bodies they saw in the sky. Some names we know today come from the names of Scandinavian gods.
Tiu’s day: Mars, the Roman god of war, was adopted in Scandinavian mythology as the warrior Tiu or Tiw.
Woden’s day: the Roman god mercury became the Scandinavian god Woden.
Thor’s day: like the Roman god Jupiter, Thor was a thunder god.
Freyja’s day: like Venus, freyja or Frigg was the goddess of love.