I know exactly what you mean, back in '95 a couple of us were using AIM on my crap dialup connection and I was screwing around and said coo instead of cool, mostly to annoy this one guy Ian. The other people the room were asking what it meant, my friend started doing it too, "that's coo", "ya, coo", etc. Ian laughed and said we sounded like a bunch of doves or something. Couple months later, everyone's saying it. I too have no proof but my friends remember us doing it and we still get a laugh about the whole thing.