You and your mother, the same always
Haha! Del Potro was the one who said that, wasn't he? Then Murray explained at length how "your mum" insults are unacceptable in tennis. Although they seem to have made up since then.
It does seem to be "fucking something." I don't think a Swiss guy would say "dolt", but I'm not gonna defend it. Whatever he said, it was directed at Murray, which makes it really poor sportsmanship. I just hope the second word wasn't an insult. I'm at a loss to explain it, because I can't see what Murray had done to deserve being shouted at.