Well, it can act as an intensifier in other languages too - "very very good" is better than "very good" and "sehr sehr gut" is the same.
I'm not convinced about the childish thing, unless it's done with specifically childlike words - in fact, usually I'd say that more childlike would be similar and rhyming words (can't think of band names other than Oingo Boingo, but stuff like that and 'Mellow Yellow' etc). Repetition in band names does tend to be poeticism without meaning, though, which, to be honest, is pretty much what lyrics are.
― emil.y, Saturday, 5 March 2011 16:48 (thirteen years ago) link