[ClearCase_guy]

You are correct. The saying is appropriate for that type of snare.

I believe the original saying goes back to Shakespeare and I believe the term "petard" got applied to that type of animal trap only in the 19th century. But that's a quibble.

[bill1952]

Yes, you are right about Shakespeare:

Hamlet, act III, scene 4, lines 206 and 207: "For 'tis sport to have the engineer Hoist with his own petard."

Which certainly supports the bomb explanation of the phrase!