Grammelot: A type of gibberish spoken in satirical theater, especially Commedia dell'Arte. It incorporates elements of onomatopoeia (imitation of sounds, such as "whoosh") and macaronisms (words formed from a mixture of languages).
The international troupe Cirque de Soleil has invented its own form of Grammelot, which it calls Cirquish.
The origin and history of the word "Grammelot" are unclear. Here's one hypothesis, and a short lexicon, from a Grammelot practitioner. For other views, read some interesting Language Log posts on Grammelot.