Spread via the Lower Rhineland from Middle Low German dingesdach and Middle Dutch dinsendach (both with variants). Probably from *þingsus-dagaz (“Day of Thingsus”). Thingsus is the attested Latin name of a Germanic god who may or may not be the same as Tiw (Old High German Ziu, for whom compare Ziestag). Further particulars unsettled. Another theory is that it is the “Day of the Thing”. Dienstag is cognate with Dutch dinsdag.
- (days of the week) Tag der Woche; Montag, Dienstag, Mittwoch, Donnerstag, Freitag, Samstag, Sonntag (Category: de:Days of the week)
- Dienstag in Duden online