Fast and Loose

[My Good Babushka]

The expression "fast and loose" came from a medieval street game played by a trickster, wherein a coiled belt was laid on the table with what appeared to be a knotted loop in the center. A mark was invited, for a fee, to stab a knife into the knot, striking it "fast" to the table. The trickster easily lifted the belt and the sucker lost his money, since the belt was actually still "loose" owing to the configuration of the trick knot.