From tsedert, a variant form of sedert (pronounced with initial z-), from Middle Dutchseder(“thenceforth, since then”). Originally a Hollandic dialectal form, the other dialects used sider (which would have become modern *sijder(t)), from Old Dutchsīther, from Proto-Germanic*sīþiz(“later”), a comparative form of *sīþuz(“late”) (from which the rare zijd). Ultimately related to sinds.