In the English language the days of the week are named for six Germanic gods … and the Roman god Saturn.
In the Indo-European family tree of languages, English is a descendant of Germanic languages. English also inherited elements of ancient Germanic culture such as Germanic mythology. The Germanic peoples took the Roman idea of naming the days of the week for various gods, but they changed the Roman gods to Germanic gods (except one).
• Sunday is named after the Germanic goddess Sunna (aka Sól in Norse mythology). Along with her brother Máni, she was taken from their father Mundilfari and placed in the sky. Sunna is the sun, moving across the sky in her chariot. Her brother is the moon, moving across the sky in his chariot. To make sure they keep moving the gods set two wolves to chase each sibling continuously. The wolf Sköll chases Sunna. From her we get the Sun’s day, or Sunday.
• Monday is named for the Germanic god Máni, brother of Sunna (as mentioned above). He rides through the sky on his chariot and is chased by the wolf Hati. From him we get Moon’s day, or Monday.
• Tuesday is named for the one-armed Germanic god of war Týr (aka Tíw), which became Tīwes day or Tuesday.
• Wednesday is named for Odin (aka Wōden), the central god of the Germanic pantheon of gods. From him we got Wōdnes day which became Wednesday.
• Thursday has perhaps the most well-known origin. Pop culture has made the hammer-wielding god of thunder & lightning Thor (aka Þunor – pronounced “Thunor”) one of the most well known Germanic gods. His name is also the origin for our word thunder which, in modern German, is “donner” and gives us Donnerstag or “Thunder day / Thursday.” In English Thor’s day became Thursday.
• Friday is named for the Germanic goddess Frigg (aka Frīja, or Frea). She was the wife of Odin and, given a good deal of mythological overlap, she and the goddess Freyja may have been the same character at one point. Frigg’s day became Friday.
• Saturday is the odd man out. In the West Germanic languages Saturday comes from the Latin “Saturni dies” or Saturn’s day, named for the Roman god Saturn. Around Scandinavia however, in Norse Germanic languages, Saturday is called by different variations of lørdag or laugardagur, which translates as Bath / Laundry Day.
Added info: The reindeer pair Donder & Blitzen from the Christmas story Rudolph the Red-Nosed Reindeer, come from the Germanic words for thunder & lightning.