The days do match up with the planets, but most of the the actual names are from Norse gods: Tuesday = Tyr's day (the god of war) Wednesday = Woden's day (or Odin, the chief god) Thursday = Thor's day (the god of thunder) Friday = Frija's day (the goddess of love)

Sunday = Sun （日） Monday = Moon （月） Tuesday = Mars （火星） Wednesday = Mercury （水星） Thursday = Jupiter （木星） Friday = Venus （金星） Saturday = Saturn （土星） Peachey is right. Tyr is Nordic/Germanic. Mars is Roman. Both mean the God of War. Same with Thor and Jupiter; Frija and Venus. Didn't know about Odin and Mercury though. But it is true!

here it is rest day...