[Petronski]

pe·tard    ( P )  Pronunciation Key  (p-tärd)
n.

1. A small bell-shaped bomb used to breach a gate or wall.
2. A loud firecracker.

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[French pétard, from Old French, from peter, to break wind, from pet, a breaking of wind, from Latin pditum, from neuter past participle of pdere, to break wind. See pezd- in Indo-European Roots.]

Word History: The French used pétard, “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.” The French noun pet, “fart,” developed regularly from the Latin noun pditum, from the Indo-European root *pezd-, “fart.”

[Deb]

exactly. One isn't blown up on one's own bomb, but "by" or "with". People who use "on" obviously don't know what they're saying.

[dr_pat]

The French used pétard, “a loud discharge of intestinal gas...” “To be hoist by one's own petard,” a now proverbial phrase apparently originating with Shakespeare's Hamlet...

Sounds to me like a typical earthy Shakespearian image, rising skyward on (or hoisted skyward by) a blast of one's own intestinal gas.