Tuesday comes from Old English Tiwesdæg meaning “Tiw’s day”, Tiw being a Proto-Germanic form of Tyr, the Norse god of law, justice, the sky, and war. It seems to derive from PIE *deywós (god) (the same source as Zeus and Jupiter), a derivative of root *dyew- (to be bright; sky, heaven). In the nursery rhyme, Monday’s Child, Tuesday’s child is full of grace.
Origin: Proto-Indo-European
Names Throughout the Ages 