And Friday. Well, the only planet left is Venus, goddess of love. The Anglo-Saxen goddess of love was Frigg and this is her day. But whether Venus or Frigg day, everybody loves it.
Monday is moon day. Roman mythology had the moon goddess Luna which why French has Lundi, Spanish Lunes, but here English substituted it with its own old English word for moon, Mona.
The planets were named for gods of Roman mythology. In Latin Saturday was dies Saturni, day of Saturn, god of agriculture. English stuck with that idea for Saturday.
In ancient Latin Sunday was Dies Solis for the Sun God but in Christian era it was renamed Domonicas for lord's day.
Most of the Romance languages use a desendant of that but in English and Germanic languages it is still named for the sun.
I bet you can guess who Thursday is named for. In ancient Rome Jupiter or Jove, the sky god of thunder, a pretty good match for Thor. #bookmark
Tuesday is Mars day. But the Anglo-saxons had their own sky god of war named Tiw or Tyr in Norse Mythology known as the one-handed war god (due to his hand having been bitten off by a wolf).
The reason that Wednesday is spelled so funny is because it's actually Woden's day. Woden was the big guy of Germanic mythology and the creator of the universe and master of hunting and war while the Roman god Mercury was a mere messenger to the gods.