Don't Be Insulted When Someone Calls You...

... an ass. Just assume your would-be detractor is saying you're a wild one, known as an onager. One of the renowned Sassanid Great Kings, Bahram V was known as Bahram the Onager. As Giusto Traina explains in 428 AD, the epithet signified that Bahram was powerful and great, because the onager itself was the fastest animal in the desert and could produce such intense bursts of speed that when the Greeks invented a siege machine that launched large stones, they named it the onager (according to Traina).

I think it was actually the Romans (before those living in the Roman Empire might be known as Greeks) who named the device onager. If you have more information about this device of siege warfare, please post in the comments.