curious"Hoist with his own petard"
The correct phrase is "Hoisted by his own petard." A petard is a keg of gunpowder that would be placed against castle/fortress gates and lit. The fuses were rather unreliable -- so an unlucky, or just plain incompetant, engineer could be hoisted (blown up) by his own petard.
What are ones you've noticed or that irritate you?
