I know what it means - (I did it to myself earlier today, LOL) but I was wondering just what a petard is.
A petard was a device containing explosives used to breach a wall or doors etc. It can also mean a type of explosive firework. The expression 'hoist with your own petard' means to become a victim of your own schemes etc. The word derives from the French verb 'peter', from the Latin 'Pedere', meaning to break wind. (HONESTLY!!!) A footnote - in the UK we sometimes refer to a short coat or jacket as a 'bum-freezer'; the French call it a 'pet-en-l'air' - literally 'fart in the air'. I hope this helps!!
Try William Shakespeare for the phrase. Sorry I can't remember the play, but that should give you a start as to the origin of the expression.
