batyoudaoicibaDictYouDict[bat 词源字典]
bat: Bat as in ‘cricket bat’ [OE] and bat the animal [16] come from entirely different sources. Bat the wooden implement first appears in late Old English as batt ‘cudgel’, but it is not clear where it ultimately came from. Some have postulated a Celtic source, citing Gaulish andabata ‘gladiator’, which may be related to English battle and Russian bat ‘cudgel’, but whatever the word’s origins, it seems likely that at some point it was influenced by Old French batte, from battre ‘beat’.

The flying bat is an alteration of Middle English backe, which was borrowed from a Scandinavian language. The word is represented in Old Swedish natbakka ‘night bat’, and appears to be an alteration of an earlier -blaka, as in Old Norse lethrblaka, literally ‘leatherflapper’. If this is so, bat would mean etymologically ‘flapper’, which would be of a piece with other names for the animal, particularly German fledermaus ‘fluttermouse’ and English flittermouse, which remained a dialectal word for ‘bat’ into the 20th century.

It is unusual for the name of such a common animal not to go right back to Old English; in this case the Old English word was hrēremūs, which survived dialectally into the 20th century as rearmouse.

=> battle[bat etymology, bat origin, 英语词源]
bat (n.1)youdaoicibaDictYouDict
"a stick, a club," Old English *batt "cudgel," perhaps from Celtic (compare Irish and Gaelic bat, bata "staff, cudgel"), influenced by Old French batte, from Late Latin battre "beat;" all from PIE root *bhat- "to strike." Also "a lump, piece" (mid-14c.), as in brickbat. As a kind of paddle used to play cricket, it is attested from 1706.

Phrase right off the bat is 1888, also hot from the bat (1888), probably a baseball metaphor, but cricket is possible as a source; there is an early citation from Australia (in an article about slang): "Well, it is a vice you'd better get rid of then. Refined conversation is a mark of culture. Let me hear that kid use slang again, and I'll give it to him right off the bat. I'll wipe up the floor with him. I'll ---" ["The Australian Journal," November 1888].
bat (n.2)youdaoicibaDictYouDict
flying mammal (order Chiroptera), 1570s, a dialectal alteration of Middle English bakke (early 14c.), which is probably related to Old Swedish natbakka, Old Danish nathbakkæ "night bat," and Old Norse leðrblaka "leather flapper" (for connections outside Germanic, see flagellum). If so, the original sense of the animal name likely was "flapper." The shift from -k- to -t- may have come through confusion of bakke with Latin blatta "moth, nocturnal insect."

Old English word for the animal was hreremus, from hreran "to shake" (see rare (adj.2)), and rattle-mouse is attested from late 16c., an old dialectal word for "bat." Flitter-mouse (1540s) is occasionally used in English (variants flinder-mouse, flicker-mouse) in imitation of German fledermaus "bat," from Old High German fledaron "to flutter."

As a contemptuous term for an old woman, perhaps a suggestion of witchcraft (compare fly-by-night), or from bat as "prostitute who plies her trade by night" [Farmer, who calls it "old slang" and finds French equivalent "night swallow" (hirondelle de nuit) "more poetic"].
bat (v.1)youdaoicibaDictYouDict
"to move the eyelids," 1847, American English, from earlier sense of "flutter as a hawk" (1610s), a variant of bate (v.2) on the notion of fluttering wings. Related: Batted; batting.
bat (v.2)youdaoicibaDictYouDict
"to hit with a bat," mid-15c., from bat (n.1). Related: Batted; batting.