"project, overhang," apparently a Shakespearean back-formation (in "Hamlet," 1602) from beetle-browed, from Middle English bitelbrouwed "grim-browed, sullen" (mid-14c.), from bitel "sharp-edged, sharp" (c. 1200), probably a compound from Old English *bitol "biting, sharp" (related to bite (v.)), + brow, which in Middle English meant "eyebrow," not "forehead." The meaning "to overhang dangerously" (of cliffs, etc.) is attested from c. 1600. Related: Beetled; beetling.