A petard is a Renaissance-era bomb, basically a big firecracker: a box
or small barrel of gunpowder with a fuse attached. Those hissing
black exploding spheres that you see in Daffy Duck cartoons are
petards. Outside of cartoons, you are most likely to encounter the
petard in the phrase "hoist with his own petard", which is from
Hamlet. Rosencrantz and Guildenstern are being sent to
England with the warrant for Hamlet's death; Hamlet alters the warrant
to contain R&G's names instead of his own. "Hoist", of course,
means "raised", and Hamlet is saying that it is amusing to see someone
screw up his own petard and blow himself sky-high with it.
This morning I read in On Food in
Cooking that there's a kind of fried choux pastry called
pets de soeurs ("nuns' farts") because they're so light and
delicate. That brought to mind Le Pétomane, the world-famous
theatrical fartmaster. Then there was a link on reddit titled "Xmas
Petard (cool gif video!)" which got me thinking about petards, and it
occurred to me that "petard" was probably akin to pets, because
it makes a bang like a fart. And hey, I was right; how delightful.
Another fart-related word is "partridge", so named because its call
sounds like a fart.
[Other articles in category /lang/etym]