I have similar funny story. One guy I train with always wears a mouth piece and mumbles a lot while he rolls, he's very good, but a lot smaller than me. One time I'm going a little harder than usual and he starts cursing under his breath, saying dammit, or shit when I sweep him or pass his guard, I think he even said 'fucker' when I got mount. I thought this was weird but I wasn't hurting him or anything so I mostly just ignored it. After a while I get an arm bar, but he gets the RNC style grip to defend. As I'm trying to break his grip he starts saying 'crap'. He says it three times, a little louder each time; crap, Crap, CRAP. Finally, just as I get the arm free I realize he has been saying 'tap' not 'crap', and it's just his mouth piece distorting the word. Needless to say that was a little awkward afterward.