Thursday
Old English Thu(n)resdæg ‘day of thunder’, named after Thunor or Thor, the Germanic god of thunder; translation of late Latin Jovis dies ‘day of Jupiter’, Thor being equated with the Roman god Jupiter. Compare with Dutch donderdag and German Donnerstag .
wiktionary
From Middle English Thursday, Thuresday, from Old English þursdæġ, þurresdæġ(“Thursday”), possibly from a contraction of þunresdæġ(“Thursday”, literally “ Thor's day”), but more likely of North Germanic origin, from Old Norse þōrsdagr or Old Danish þūrsdag(“Thursday”); all from Proto-West Germanic *Þunras dag(“day of the thunder god”). Compare West Frisian tongersdei, German Low German Dunnersdag, Dutch donderdag, German Donnerstag, Danish torsdag. More at thunder, day.
A calque of Latin diēs Iovis ( diēs Jovis), via an association ( interpretātiō germānica) of the god Thor with the Roman god of thunder Jove (Jupiter).
etymonline
Thursday (n.)
fifth day of the week, Old English þurresdæg, a contraction (perhaps influenced by Old Norse þorsdagr) of þunresdæg, literally "Thor's day," from Þunre, genitive of Þunor "Thor" (see thunder (n.)); from Proto-Germanic *thonaras daga (source also of Old Frisian thunresdei, Middle Dutch donresdach, Dutch donderdag, Old High German Donares tag, German Donnerstag, Danish and Swedish Torsdag "Thursday"), a loan-translation of Latin Jovis dies "day of Jupiter."
Roman Jupiter was identified with the Germanic Thor. The Latin word is the source of Italian giovedi, Old French juesdi, French jeudi, Spanish jueves, and is itself a loan-translation of Greek dios hēmera "the day of Zeus."
