Hoisted by his Own Petard . . . what?

This is Steven Petrick Posting.

You may have heard the phrase (perhaps in a class on Shakespeare) "Hoisted by his own Petard". You may have heard it in conversation and, from its use, have some vague idea of its meaning, pretty much that some surprise someone was planning to spring on someone else had backfired.

The phrase is actually one that would have been understood by most soldiers in the Shakespearian age, but other than its usage (as given above) even most modern soldiers have no comprehension of what a "Petard", or how one would be "hoisted" by it.

A "Petard" was a small bomb that was used to blow open a gate, and if it happened to detonate early (powder and fuses not being all that reliable in that age, it was entirely possible that when you set a flame to light a fuse, said fuse would burn instantly rather than slowly) you would be "hoist", that is to say "lifted" into the air.

Thus "Hoisted by his own Petard" literally means "was blown up by his own explosive device".