hoist: lift up; raise or lift somebody or something up.
be hoist with your own petard: to be the victim of your own attempt to harm somebody else
(Encarta ® World English Dictionary © & (P) 1998-2004 Microsoft Corporation)
One thing I love about the internet is the easy ability to look up words and their derivations and consequently to use them precisely as well as creatively. I like to keep the dictionary at an easy click, and I keep a dictionary of my own of words and phrases that are not easily accessible otherwise and of quotations for easy reference.
Thanks, LS and AAM, for bringing this useful concept to clarity. ~S
"petard" is related to the French word for a social indiscretion -- remember "Le Petomane" (loosely translated as "The Fartiste") who wowed the Paris music halls with his gaseous performances?
Which does give you the impression that these early explosive devices weren't exactly blockbusters . . .
If you want to see a demonstration of what a petard exactly is and what it does, get the PBS video or
DVD of "By the Sword Divided," a play about the English Civil War in the seventeenth century. Toward the end of the play the Roundheads besiege a Cavalier estate and break in by exploding a petard against the estate's gate. During the same battle there's also a great demonstration of how seventeenth century mortars worked.