I have a friend who, every time he tell someone what onomatopoeia means, points out that, oddly enough, onomatopoeia is not itself onomatopoeic.
Is "heterological" a heterological adjective?
- Grelling and Nelson, 1908.
It would be very difficult to do that since onomatopoeia is a concept and concepts don't make sounds.
http://en.wikipedia.org/wiki/Cliche#Origin
A world like onomatopoeia being onomatopoeic isn't that far-fetched. Perhaps the word could be named after a very common onomatopoeia, perhaps one that has gone out of use. A word with that sort of etymology is "shibboleth" - its current meaning is derived from what was a common shibboleth.
...etc.