A petard was

an explosive device used is Ye Olde Days to blow holes in castle doors/walls during sieges.

Early explosive science being a bit primitive, the fuses weren't very reliable. So the bloke responsible for setting it up sometimes used to go up with it - he was hoist by his own petard.

FACT (though not wildilfe related)

Posted By: Old Git, May 23, 11:44:01