PC gone mad? ... sounds like it.

I think the most logical explanation is given by Quinion, being that "it is a reduplication - using the same mechanism that has given us namby-pamby and itsy-bitsy - of the standard English word gritty."
Case closed in my eyes.

What really amuses me is how valiantly and with which authority people will support there own version of a word's etymology in a conversation, as if it gave them a deeper understanding of any "true meaning' the word might have. Strangely enough, this tendency seems to be all the more solid, the more ludicrous, abstract or iffy the etymological explanation is.
I recently discussed the origins of the word 'posh' (discussed previously here I believe) with someone who was utterly certain that it was short for "Port Out, Starboard Home". I suggested that this was possibly just a story, if a really good one, and that it had absolutely no proof to support it. This was out of the question for my conversation partner, they had heard it on the radio and many people believed it. For me it once again reinforced that the notion of truth as absurd outside the realms of theological and philosophical contexts. For if one person believes something, they're a loony and it's a lie; if a group does they're a cult and the notion is mystical nonsense, and if 80% of people do then it's truth.