There was a chap at school with me who, whenever a crowd was gathered at a sporting event or somesuch, 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.
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.
Echo was the nymph who loved Narcissus and, on rejection, pined away until she was only a sound. Lalia was 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.
The Inky Fool counts his fishes