Etymology
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petard (n.)

1590s, "engine of war consisting of a small, attachable bomb used to blow in doors and gates and breach walls," from French pétard (late 16c.), from French péter "break wind," from Old French pet "a fart," from Latin peditum, noun use of neuter past participle of pedere "to break wind," from PIE root *pezd- "to fart" (see feisty). Surviving in figurative phrase hoist with one's own petard (or some variant) "caught in one's own trap, involved in the danger one meant for others," literally "blown up with one's own bomb," which is ultimately from Shakespeare (1605):

For tis the sport to haue the enginer Hoist with his owne petar ["Hamlet" III.iv.207].

For the verb, see hoist. The thing itself was rendered obsolete by the development of bombs; it seems to have had a reputation for backfiring. Related: Petardier.

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pediculosis (n.)

"lice infestation," 1809, with -osis + Latin pediculus, diminutive of pedis "a louse," said in some sources to be akin to pedere "to break wind" (see petard) on notion of "foul-smelling insect" [Watkins]. But de Vaan traces it to a PIE *pesd- "annoying insect" and compares Avestan pazdu- "beetle, maggot." Pedicule "louse" is attested in Middle English (early 15c.).

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hoist (v.)

1540s, "to raise, lift, elevate," especially with a rope or tackle, earlier hoise (c. 1500), from Middle English hysse (late 15c.), which probably is from Middle Dutch hyssen (Dutch hijsen) "to hoist," related to Low German hissen and Old Norse hissa upp "raise," Danish heise, Swedish hissa. A nautical word found in most European languages (French hisser, Italian issare, Spanish izar), but it is uncertain which coined it. Related: Hoisted; hoisting. In phrase hoist with one's own petard, it is the past participle.

For 'tis the sport, to have the engineer
Hoist with his own petar: and it shall go hard
But I will delve one yard below their mines,
And blow them at the moon: O 'tis most sweet,
When in one line two crafts directly meet.
["Hamlet," Act III, Scene iv]

Meaning "to lift and remove" was prevalent c. 1550-1750. As a noun, 1650s, "act of hoisting;" 1835, "that by which something is hoisted," from the verb.

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