köken: Borrowed from Italian ciao (“hi”), from Venetan s-ciao, sciavo (“slave”) (in particular the expression s-ciao vostro, literally meaning "(I am) your slave" but in essence meaning "your humble servant"), from Medieval Latin sclavus (“slave”). Doublet of szláv. See also the similar etymology at szervusz and alászolgája.
köken: Borrowed from Italian ciao (“hello; goodbye”), from Venetan ciao (“hello; goodbye”, literally “[I am your] servant”), from Medieval Latin sclavus (“Slav; slave”). Doublet of sklavo and slavo. Colloquial use likely reinforced by German servus (“hello; goodbye”), which is used similarly.