beetle (n.1) Look up beetle at
insect of the order Coleoptera, Old English bitela "beetle," apparently originally meaning "little biter, biting insect," from bitel "biting," from Proto-Germanic *bitan, from PIE root *bheid- "to split," with derivatives in Germanic referring to biting.

By normal evolution it would be *bittle, but it seems to have been influenced by beetle (n.2). Sometimes applied to soft insects, as black beetle, an old name for the cockroach. As a nickname for the original Volkswagen car, 1946, translating German Käfer.
beetle (n.2) Look up beetle at
"heavy wooden mallet used to drive wedges, pack earth, etc.," Old English bietl "mallet, hammer," from Proto-Germanic *bautilo-z, from *bautan "to beat," from PIE root *bhau- "to strike" (see beat (v.)).
beetle (v.) Look up beetle at
"project, overhang," apparently a Shakespearean back-formation (in "Hamlet," 1602) from 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." Meaning "to overhang dangerously" (of cliffs, etc.) is from c. 1600. Related: Beetled; beetling.