What language does onomatopoeia come from?

It's a combination of two Greek words:

* ὀνοματοποιεῖν (onomatopoieîn) - "to make a name"

* ὄνομα (ónoma) - "name"

* ποιεῖν (poieîn) - "to make"

So, literally, onomatopoeia means "to make a name by imitating a sound".