"small piece," c. 1200; related Old English bite "act of biting," and bita "piece bitten off," which probably are the source of the modern words meaning "boring-piece of a drill" (the "biting" part, 1590s), "mouthpiece of a horse's bridle" (mid-14c.), and "a piece (of food) bitten off, morsel" (c. 1000). All from Proto-Germanic *biton (source also of 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."
Meaning "small piece, fragment" of anything is from c. 1600. Sense of "short space of time" is 1650s. Theatrical bit part is from 1909. Money sense "small coin" in two bits, etc. is originally from the U.S. South and the West Indies, in reference to silver wedges cut or stamped from Spanish dollars (later Mexican reals); transferred to "eighth of a dollar."
type of boring tool, mid-14c., gymbelette, from Anglo-French and Old French guimbelet, guibelet (12c., Modern French gibelet), which is probably of Germanic origin, perhaps from Middle Dutch wimmelkijn (with substitute of French diminutive suffix), diminutive of wimmel "auger, drill," which is perhaps from a nasalized form of PIE root *weip- "to turn" on the notion of "That which turns in boring." Middle English also had wimble in the same sense (mid-13c.), probably from an Old North French form of the same word.
As the name of a cocktail made with gin or vodka and (Rose's) lime juice, by 1927, apparently originally nautical, presumably from its "penetrating" effects on the drinker (a gimlet was the tool used to tap casks). There also was a British Navy surgeon named Gimlette at the turn of the 20th century who was active in health matters. Popularized in the U.S. during prohibition as being quick and easy to mix, and the lime masked the scent.
"to put a mark on," Old English mearcian (West Saxon), merciga (Anglian) "to trace out boundaries;" in late Old English "make a mark or marks on," from Proto-Germanic *markojan (source also of Old Norse merkja, Old Saxon markon "appoint, observe, remark," Old Frisian merkia, Old High German marchon "to limit, plan out," German merken "to mark, note," Middle Dutch and Dutch merken "to set a mark on"), from the root of mark (n.1).
Influenced by the Scandinavian cognates. Meaning "to have a mark" is from c. 1400; that of "to notice, observe" is late 14c. Figurative sense of "designate as if by placing a mark on," hence "to destine," is from late Old English. Meaning "be a noteworthy feature of" is by 1660s. To mark time (1833) is from military drill, originally "move the feet as if marching but remain in place."
The verbs in Romanic are from the nouns, which are early borrowings from Germanic: Old French merchier "to mark, note, stamp, brand," French marquer "to mark," Spanish marcar, Italian marcare.