The name of this curse is related to the popular "mumbo-jumbo" magical phrase Abracadabra, which is actually of Aramaic origin: avra (or abara) means "I will create"; k'davra means "as I speak". Thus, abracadabra, "I will create as I speak". Similarly, avada means "I will destroy". So, in Rowling's world, the killing curse literally means "I will destroy as I speak", a pretty fair description of its effects.
A footnote in some editions of the Vietnamese translations of the Harry Potter books state a false etymology: "avatar cadaver": see [1].
Also, Romanian translations use Abracadabra as Avada Kedavra. The reasons for this is believed to be from the latin word cadaver, which can mean corpse.
During an audience interview at the Edinburgh Book Festival (15 August 2004) Rowling said:
"Does anyone know where avada kedavra came from? It is an ancient spell in Aramaic, and it is the original of abracadabra, which means “let the thing be destroyed”. Originally, it was used to cure illness and the “thing” was the illness, but I decided to make it the “thing” as in the person standing in front of me. I take a lot of liberties with things like that. I twist them round and make them mine." [2]