"thorny shrub, heath," 1540s, variant of Middle English brere, from Old English brer (Anglian), brær (West Saxon) "brier, bramble, prickly bush," which is of unknown origin. Briar is the most recent variant (c. 1600). Originally used of prickly, thorny bushes in general, now mostly restricted to wild rose bushes (sweet briar). Used figuratively (in plural) for "troubles" from c. 1500. French bruyère "heath plant" (source of brier (n.2)) is considered to be unrelated.
type of tobacco pipe introduced to England c. 1859 and made from the root of a certain shrub (Erica arborea) in the south of France and Corsica, 1868, from French bruyère "heath plant," from Old French bruiere "heather, briar, heathland, moor" (12c.), from Gallo-Roman *brucaria, from Late Latin brucus "heather," from Gaulish *bruko- (compare Breton brug "heath," Welsh brwg, Old Irish froech). Form altered in English by influence of brier (n.1).