My sickest was in the next moment, when I unbreached my gun and found there was no shell in either barrel!
Old English bryce "breach, fracture, a breaking," from brecan (see break), influenced by Old French breche "breach, opening, gap," from Frankish; both from Proto-Germanic *brecho, *bræko "broken," from PIE root *bhreg- "to break" (see fraction). Figurative sense of "a breaking of rules, etc." was in Old English Breach of contract is at least from 1660s.
1570s, from breach (n.). Related: Breached; breaching.