Used in the dice game craps. It means to cover the shooter's bet, that is, bet that he will lose.
I dreamed last night I got on the boat to Heaven
And by some chance I had brought my dice along,
And there I stood, and I hollered,
"Someone fade me,"
But the passengers they knew right from wrong
For the people all said,
"Sit down, sit down you're rockin' the boat."