The French used p�tard, �a loud discharge of intestinal gas,� for a kind of infernal engine for blasting through the gates of a city. �To be hoist by one's own petard,� a now proverbial phrase apparently originating with Shakespeare's Hamlet (around 1604) not long after the word entered English (around 1598), means �to blow oneself up with one's own bomb, be undone by one's own devices.�