Linguistics

Yes, albeit indirectly - Italian borrowed it from Venetian sciao /stʃao/, that underwent the following sound changes:

• Latin /kl/ ⟨CL⟩ → */kj/ → Venetian /tʃ/. Regular.
• Latin /wu/ ⟨VV⟩ → Venetian /o/. Sometimes it fortifies to /vo/ instead, but there are other words where this happens (see e.g. pavonem "peacock" → paon)

Then Italian dropped the /s/ in the borrowing because, while /stʃ/ is a legal cluster in Venetian, it isn't in Italian.

The semantic shift might look weird, but it pops up also in Austro-Bavarian and German "servus!" (hello) and Polish "serwus" (hello). Wiktionary mentions that the German greeting is from Mediaeval "seruus humillimus, domine spectabilis"; or "[I am a] humble servant, o notable lord", odds are that Venetian "sciao" is the same.

Note that the purely native Italian cognate would be schiavo /skjavo/ "slave".

EDIT: Dieguito answered as I wrote this answer, but I'm keeping it for further info.

Yes, passing through the Venetian vulgar where the "cla" cluster which evolved to modern Italian "-chia-" [ki̯a] is further palatalized to "cia" [t͡ʃa].

The original salute was meaning is "I am at your command". In that region we still today, even it it's rare / something that only elderly people do, use the form "mandi", derived from "comandi" (i.e. again "at your commands").