Buddy Hacket told this one many years ago.
A man was ice fishing with absolutely no luck. He did notice that another ice fisherman nearby was doing extremely well. He decided to talk to him and find out his secret.
So, he asks, "How do you catch so many fish? I'm not catching anything."
The successful fisherman mumbles and answer, "Mmmum muum mmmh."
The man doesn't understand a work he said, so he asks again.
The response was the same mumbling answer.
I poor fisherman says, "I'm sorry, I still can't understand you."
So, the successful fisherman spits a big wad of something into his hands as replies, "You gotta keep the worms warm!"