Breech
Old English brēc (plural of brōc, of Germanic origin; related to Dutch broek ), interpreted as a singular form. The original sense was ‘garment covering the loins and thighs’ (compare with breeches), hence ‘the buttocks’ (breech (sense 2 of the noun), mid 16th century), later ‘the hind part’ of anything.
wiktionary
From Middle English breche, from Old English brēċ, from Proto-Germanic *brōkizpl, from Proto-Germanic *brōks(“clothing for loins and thighs”). Cognate with Dutch broek, Alemannic German Brüch, Swedish brok.
etymonline
breech (n.)
"back part of a gun or firearm," 1570s, from singular of breeches (q.v.) in the sense "lower part of the body," hence "the hinder part of anything" (especially the part of a cannon or firearm behind the barrel). Breech-loader is from 1858.
breech (v.)
late 15c., "put in breeches," from breeches. Meaning "fit a gun with a breech" is from 1757, from breech (n.). Related: Breeched; breeching.
