Hoist by Your Own Petard

This one is a direct Shakespeare coinage, from Hamlet: "For 'tis the sport to have the engineer hoist with his own petard." A petard was a real, primitive explosive device, a small bomb packed into a metal or wooden case, used to blow open city gates and castle walls. "Hoist" is an old form of "hoise," meaning lifted or blown upward. Put together, the image is of a bomb-maker blown into the air by his own bomb, close-in irony rather than distant misfortune. There's also a buried joke: "petard" comes from French pétard, ultimately from a Latin verb meaning "to break wind," so Shakespeare's audience likely caught a second, cruder meaning too.