To our
knowledge and
belief, the use of
raspberry to signify the old
intermittently
plosive bilabial fricative, that is to say, the
Bronx cheer, is the only example of
chivvy (or
Cockney rhyming slang) in common usage in
American English.
E. Cobham Brewer tells us that raspberry means the heart in chivvy on the logic that heart rhymes with raspberry tart. So it does. And of course, your wily Cockney syncopates the tart part.
Raspberry tart also rhymes with something both ruder and more apt, something that blowing the raspberry is or was originally meant to imitate. What is interesting about this is that the term has fossilized: the euphemism has survived without bringing its vulgar referent along with it.
Well, fart on that, we say.