“To be hoist by one’s own petard,” is a now proverbial phrase apparently originating with Shakespeare’s Hamlet (around 1604) not long after the word entered English (around 1598).

It means “to blow oneself up with one’s own bomb, be undone by one’s own devices.”

The French developed a kind of infernal engine, named the Petard, only about a decade before Shakespeare used the hoisting phrase in Hamlet, for blasting through the gates of a city. The French noun pet, “fart,” developed regularly from the Latin noun pēditum, from the Indo-European root *pezd-, “fart.”

During WWII, the British had a munition also called the Flying Dustbin. which was a spigot mortar. It fired a 40-pound (18 kg) finned bomb at pillboxes and other concrete obstacles, to destroy them – but that was long after Hamlet was published.

its a form of bomb on a spike

when lit a man would run at the castle doors his side were at war with and ram it into the doors

but occasionaly his clothes would get stuck to the spike , or the fuse would be so short so the opposition could not extinguish it that he would be killed in the ensuing explosion

and so the expression ” hoist by his own pitard ”

all the best

Ian

RE:
"Hoisted on his own pitard" What is a pitard and what does the saying mean?