ˁarrādat- - an engine of war that casts a stone to a long distance, similar to that called by the Romans onager (BK 2 212, Lane 1998)

This usage is probably a calque from Grk. onagros, Lat. onager (so DNWSI), but it is worth noting that the meaning ‘a mechanical device’ (in particular, ‘a part of the battering ram’) is attested already for Akk. imēru (CAD I 114–5).