The origin of the names of the days of week. Most of them are derived from old English with other languages integrating them into their cultures:
Monday: It’s roots are translated to Moon-day.
Tuesday: Derived from Tyr’s day; Norse God of War (also related to Roman God of war).
Wednesday: Found to be related to Wodan/Odin, Norse God. Also, related to Mercury, Roman messenger God.
Thursday: Derived from Thor’s day. Thor was the Norse God of lightning or Chris Hemsworth ( 😛 )
Friday: Day of Frigg and Freya; Goddesses in Norse mythology. Frigg was wife to Odin/Wodan and Freya was goddess of women.
Saturday: Day of Saturn; Roman God.
Sunday: Originally “Solday”, it is the day of the sun.