You mean like, why is Monday called Monday, Tuesday called that, etc.?
If you mean this, in English they were stolen from the Romans and stuck a bunch of Norse god stuff over it by the originators of the English dialect, Germanic tribes.
Monday = (Roman) Moon's Day
Tuesday = (Norse) Tyr's Day
Wednesday = (Norse) Woden's Day
Thursday = (Norse) Thor's Day
Friday = (Norse) Frige's Day
Saturday = (Roman) Saturn's Day
Sunday = (Roman) Sun's Day