beetleyoudaoicibaDictYouDict[beetle 词源字典]
beetle: English has three separate words beetle. The commonest, beetle the insect, comes from Old English bitula, which was a derivative of the verb bītan ‘bite’: beetle hence means etymologically ‘the biter’. Beetle ‘hammer’, now largely restricted to various technical contexts, is also Old English: the earliest English form, bētel, goes back to a prehistoric Germanic *bautilaz, a derivative of the verb *bautan, from which English gets beat (the cognate Old Norse beytill meant ‘penis’).

The adjective beetle [14], as in ‘beetle brows’, and its related verb are of unknown origin, although it has been speculated that there is some connection with the tufted antennae of certain species of beetle, which may suggest eyebrows.
=> bite; beat[beetle etymology, beetle origin, 英语词源]
beetle (n.1)youdaoicibaDictYouDict
type of insect, Old English bitela "beetle," literally "little biter," from bitel "biting," related to bitan "to bite" (see bite). As a nickname for the original Volkswagen car, 1946, translating German Käfer.
beetle (v.)youdaoicibaDictYouDict
"project, overhang," c. 1600, back-formation 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, + brow, which in Middle English meant "eyebrow," not "forehead." Meaning "to overhang dangerously" (of cliffs, etc.) is from c. 1600. Related: Beetled; beetling.
beetle (n.2)youdaoicibaDictYouDict
beating tool, Old English bietel, from Proto-Germanic *bautilo-z, from *bautan "to beat" (see beat (v.)).