[Carl in Tampa]

Someone recently posed the question, "What is a petard?"

A petard was a small bomb used to breach a gate or wall in early warfare.

The phrase, "Hoist with his own petar..." was originated by Shakespeare, the originator of many of our English words and phrases.

It appears in the play Hamlet, when Hamlet's uncle, the King of Denmark, plots with two of Hamlet's classmates to take a letter to the King of England instructing that Hamlet should be killed. Hamlet gives the classmates a substitute letter to the King of England instructing that the classmates should be killed.

Thus, reasons Hamlet, "the engineers" (of his destruction) will be "hoist" (blown up) by their own "petar" (bomb.) The word later became petard.

So, colloquially, the term, "Hoist with his own petar" simply means "to be undone by a means by which one intended to harm someone else."