Etymology: Old English brú (feminine), inflected on the type of an Old Germanic brûâ- strong feminine, but probably only an Old English accession to the â- declension of a West Germanic or primitive Old English brú of the type of cú , sú < Old Germanic *brû-s (= Sanskrit bhrū-s eye-brow, Greek ὀϕρύς ). The original sense appears to have been ‘eye-brow’, but it must have been extended at an early date from the hair over the eyes to that on the eye-lids, the ‘eye-lashes’, for this was the normal sense in Old English, the eye-brows being distinguished as ofer-brúa i.e. over-eye-lashes, or otherwise contextually. From the eye-lashes, the name appears to have been transferred step by step to the eye-lids, the eye-brows, the prominences of the forehead, and finally to the forehead as a whole. See also bree n.¹, and compare beetle-browed adj. at beetle adj. 1a. Old Norse brú feminine ‘bridge’ was perhaps the same word, with a transferred sense; but the Old Norse word actually used for ‘eye-brow’ was brún , plural brýnn , conjectured to be a secondary form < brû- founded on the genitive plural brú-na . (Compare modern German braune brow, founded on the plural braun , brauen , Middle High German brâwen , plural of brâwe .) In the other Germanic languages *brû- is lost, and its place supplied by *bræ̂wâ- ; thus Old High German brâwa eye-lashes, obarun brâwa , ubar-brâwa , eye-brows, modern German augen-braue , -braune (see above) eye-brow, wimper , Middle High German wintbrâwe eye-lash, Dutch wenkbraauw eye-brow, all of which belong to Old Germanic *bræ̂wâ- , West Germanic brâw , Old English brǽw ; see bree n.¹ (It appears then that the English brow and German braue, Dutch braauw are not even cognate.)

Etymology: apparently < Danish or Swedish bru, Old Norse brú bridge.

Etymology: < brow n.¹