In the 1970’s I was at school with a fellow who whenever a crowd was gathered at a rugby or cricket match, would shout ‘Give us a G!’ And the crowd would chorus ‘G’. Then ‘Give us an I!’ ‘I.’ ‘Give us an R!’
It was usually halfway through that the crowd realised he was trying to make them shout Giraffe. Rather bizzarely, the fellow in question went on to be a High Court Judge.
Anyway, the technical term for the meaningless repetition of sounds is echolalia. Echolalia is what babies do when they’re learning to speak and simply repeating the words that their parents say. Echolalia is what backing singers do when they repeat the last word of the line. Echolalia is the practice of parrots.
Echolalia is a portmanteau word and derives from Echo, who was the nymph who loved Narcissus and, upon being rejected, pined away until she was only a sound. And Lalia, which is the the Ancient Greek for talk.
On the same principle you have glossolalia – speaking in tongues – and coprolalia, which is the compulsive desire to shout obscenities. It’s a more beautiful, and therefore less appropriate, way of saying Tourette’s Syndrome.