Origin & History of “Thursday”
The Romans called the fourth day of the week diēs Iovis ‘Jupiter’s day’. when the Germanic peoples took over their system of naming days after the gods, or the planets they represented, they replaced Jupiter, the Roman sky-god, with the Germanic god of thunder, Thor, whose name comes from the same source as English thunder. this produced a prehistoric Germanic *thonaras daga-, which evolved into Old English thunresdæg. The modern form Thursday is partly due to association with Old Norse thórsdagr.