Hardly, there are other commutative slangs that preceded verlan and African immigration, like louchébem (the slang of butchers). And that's just in France, it'

Hardly, there are other commutative slangs that preceded verlan and African immigration, like louchébem (the slang of butchers). And that's just in France, it's a common trope in many languages. It just happens to be much better documented in France.