early 14c., "piece of armor protecting the arm;" 1580s, "a clamp, bind, that which braces or makes firm," agent noun from brace (v.). The figurative sense of "that which braces the nerves" is by 1740; especially an alcoholic drink taken early in the morning (by 1826). Related: Bracers.

before a vowel, brachi-, word-forming element meaning "arm, of the upper arm, pertaining to the upper arm and," from Latinized form of Greek brakhion "arm," perhaps originally "upper arm," literally "shorter," from brakhys "short" (from PIE root *mregh-u- "short"), in contrast to the longer forearm.

Proto-Indo-European root meaning "short."

It forms all or part of: abbreviate; abbreviation; abridge; amphibrach; brace; bracelet; brachio-; brachiopod; brachiosaurus; brachy-; brassiere; breviary; brevity; brief; brumal; brume; embrace; merry; mirth; pretzel; vambrace.

It is the hypothetical source of/evidence for its existence is provided by: Greek brakhys "short;" Latin brevis "short, low, little, shallow;" Old Church Slavonic bruzeja "shallow places, shoals;" Gothic gamaurgjan "to shorten."

armor or guard for the forearm, early 14c., from Anglo-French vant-bras, from Old French avant-bras, from avant "before, in front of" (see avant) + bras "an arm" (see brace (n.)).