Where does “ballistra” come from?

ballistra (Late Latin) comes from Latin ballista, from Ancient Greek βαλλίστρα, from Ancient Greek βάλλω, from Proto-Hellenic *gʷəlnō.

Ancestry of “ballistra”, step by step

Step	Language	Word	Meaning
1	Latin	ballista	ballista
2	Ancient Greek	βαλλίστρα	catapult, engine of war
3	Ancient Greek	βάλλω	I throw, cast, hurl; I let fall; I strike, touch
4	Proto-Hellenic	*gʷəlnō	—