From Wikipedia
Grammelot (also known as Gromalot[1]) is a style of language used in satirical theatre, a gibberish with macaronic and onomatopoeic elements, used in association with mime and mimicry. The format dates back to the 16th century Commedia dell’arte, and some claim Grammelot to be a specific universal language (akin to Lingua franca) devised to give performers safety from censorship and appeal whatever the dialect of the audience.