Phrases you don't hear anymore:

[soldierant]

159. "Play fast and loose" goes back to medieval times

and the "fast" in it has nothing to do with speed. Grifters at fairs (which were not celebratory events primarily, but opportunities for merchants to sell to larger crowds) , then as now, had grifters. "Fast and Loose" was a game some of them used, similar in the sense of "the quickness of the hand" aspect to the "which cup is the ball under." The grifter would take a belt, often one belonging to the mark, an twist and tie it up quickly and confusingly, and challenge the mark to take a knife and drive it into a spot such that it would stay "fast" on the table when one tried to pick it up. But it would always turn out to be "loose."