bityoudaoicibaDictYouDict[bit 词源字典]
bit: There are three distinct nouns bit in English, but the two most ancient ones are probably both related ultimately to the verb bite. Bit as in ‘drill bit’ [OE] originally meant simply ‘bite’ or ‘biting’. The Old English word, bite, came from Germanic *bitiz, a derivative of the verb *bītan ‘bite’. The ‘drill bit’ sense did not develop until the 16th century.

The bit placed in a horse’s mouth is probably the same word. Bit meaning ‘small piece’ [OE] also comes from a Germanic derivative of *bītan, in this case *biton; this gave Old English bita ‘piece bitten off’. The more general sense, ‘small piece’, developed in the 16th century. The third bit, ‘unit of computer information’ [20], is a blend formed from ‘binary digit’.

=> bite[bit etymology, bit origin, 英语词源]
bit (n.1)youdaoicibaDictYouDict
"small piece," c. 1200; related Old English bite "act of biting," and bita "piece bitten off," probably are the source of the modern words meaning "boring-piece of a drill" (1590s), "mouthpiece of a horse's bridle" (mid-14c.), and "a piece bitten off, morsel" (c. 1000). All from Proto-Germanic *biton (cognates: Old Saxon biti, Old Norse bit, Old Frisian bite, Middle Dutch bete, Old High German bizzo "biting," German Bissen "a bite, morsel"), from PIE root *bheid- "to split" (see fissure).

Meaning "small piece, fragment" is from c. 1600. Sense of "short space of time" is 1650s. Theatrical bit part is from 1909. Money sense in two bits, etc. is originally from Southern U.S. and West Indies, in reference to silver wedges cut or stamped from Spanish dollars (later Mexican reals); transferred to "eighth of a dollar."
bit (n.2)youdaoicibaDictYouDict
computerese word, 1948 abbreviation coined by U.S. computer pioneer John W. Tukey (1915-2000) of binary digit, probably chosen for its identity with bit (n.1).
bit (v.)youdaoicibaDictYouDict
past tense of bite.