Tschüss etymology

German

German word tschüss comes from Dutch and later Low German rendering of the French adieu (a dated form of "farewell" or "goodbye")

Detailed word origin of tschüss

Dictionary entry Language Definition
adieu French (fr) (Southern France) hello. (dated) goodbye, see you soon. Farewell, adieu Farewell.
adjuusjes Dutch (nl)
adjuus Dutch (nl)
adjüs Low German (nds) (in many dialects) bye
tschüss German (de) (informal) bye, cheers, ciao.