"space between the eyebrows," 1598, Mod.L., lit. fem. of adj. glabellus "without hair, smooth," dim. of glaber "smooth, bald," cognate with O.E. glæd "bright, shining, joyous" (see glad).
c.1300, from O.Fr. arche "arch of a bridge," from L. arcus (see arc). Replaced native bow (n.1). Transferred by 1590 to anything having this form (eyebrows, etc.). The verb meaning "to curve" is from 1620s. Related: Archway (1802).
"project, overhang," originally in bitelbrouwed (mid-14c.), from bitel "sharp-edged, sharp;" probably from O.E. bitela (see beetle (n.)) + brow, which in M.E. meant "eyebrow," not "forehead." It referred to shaggy eyebrows, perhaps because they suggested insect antennae. Meaning "to overhang dangerously" (of cliffs, etc.) is from c.1600.
1923, a survivor of a fad around this year for slang terms denoting "excellence" and based on animal anatomy. Also existed in the more ribald form bee's nuts. Other versions that lasted through the century are cat's whiskers (1923), cat's pajamas, cat's meow. More obscure examples are canary's tusks, cat's nuts and flea's eyebrows. The fad still had a heartbeat in Britain at the end of the century, as attested by the appearance of dog's bollocks in 1989. Bee's knee was used as far back as 1797 for "something insignificant."
words for "eyelid," "eyelash," and "eyebrow" changed about maddeningly in O.E. and M.E. (and in all the W.Gmc. languages). Linguists have untangled the knot into two strands: 1. O.E. bræw (Anglian *brew) "eyelid," from P.Gmc. *bræwi- "blinker, twinkler" (related to Goth. brahw "twinkle, blink," in phrase in brahwa augins "in the twinkling of an eye"); the sense must have shifted before the earliest recorded O.E. usage from "eyelash" to "eyelid." 2. O.E. bru "eyelash," from P.Gmc. *brus "eyebrow," from PIE base *bhrus (cf. Skt. bhrus "eyebrow," Gk. ophrys, O.C.S. bruvi, Lith. bruvis "brow," O.Ir. bru "edge"). The sense must have been transferred in O.E. at an early date from "eyebrow" to "eyelash." Lacking a distinctive word for it, the Anglo-Saxons called an eyebrow ofer-bru, and in early M.E. they were known as uvere breyhes or briges aboue þe eiges. By c.1200, everything had moved "up." Bru/brouw (from bræw) became "eyelid;" and brew/breow (from O.E. bru) became "eyebrow." It remained the word for "eyebrow" in Scottish and northern English, where it naturally evolved into colloquial bree. In southern English, however, M.E. bru/brouw took over the sense of "eyebrows," in the form brues, and yielded the usual modern form of the word. To make matters worse, if possible, some southern writers 15c.-17c. used bree for "eyelashes," in what OED calls "a curious reversion to what had been the original OE. sense of bru." By 1530s, brow had been given an extended sense of "forehead," especially with reference to movements and expressions that showed emotion or attitude. The -n- in the O.N. (brun) and Ger. (braune) forms of the word are from a gen. pl. inflection.