Other forms: petards
A petard was a very small bomb typically used for blowing holes in doors and gates, and not for bombing an entire troop or village. They had cannons for those bigger jobs.
Just like the bomb itself, the word petard has mostly fallen out of use today. It may be familiar, however, from the phrase "hoist with your own petard," which comes from Shakespeare (though he called it a petar) and means "to be hurt by your own plan to hurt someone else," "to fall into your own trap," or, essentially, "to be blown up by your own bomb."