fine (adj.)youdaoicibaDictYouDict[fine 词源字典]
mid-13c., "unblemished, refined, pure, free of impurities," also "of high quality, choice," from Old French fin "perfected, of highest quality" (12c.), a back-formation from finire or else from Latin finis "that which divides, a boundary, limit, border, end" (see finish (v.)); hence "acme, peak, height," as in finis boni "the highest good." The English word is from c. 1300 as "rich, valuable, costly;" also in a moral sense "true, genuine; faithful, constant." From late 14c. as "expertly fashioned, well or skillfully made," also, of cloth, "delicately wrought." Of weapons or edges, "sharp" from c. 1400. In reference to quality of gold and silver, late 15c.

In French, the main meaning remains "delicate, intricately skillful;" in English since c. 1300 fine has been also a general broad expression of admiration or approval, the equivalent of French beau (as in fine arts, 1767, translating French beaux-arts). Related: Finer; finest. Fine print is from 1861 as "type small and close-set;" by 1934 in the extended sense "qualifications and limitations of a deal."[fine etymology, fine origin, 英语词源]
limitation (n.)youdaoicibaDictYouDict
late 14c., from Old French limitacion and directly from Latin limitationem (nominative limitatio), noun of action from past participle stem of limitare (see limit (v.)). Phrase statute of limitations attested by 1768.
off-limits (adj.)youdaoicibaDictYouDict
"forbidden," by 1881, U.S. military academies jargon, from off (adv.) + limit (n.). Earlier (1857) it was applied to cadets, etc., who were in violation of the limitations on their movement and behavior.
string (n.)youdaoicibaDictYouDict
Old English streng "line, cord, thread, string of a bow or harp," in plural "tackle, rigging; lineage, race," from Proto-Germanic *strangiz (cognates: Old Norse strengr, Danish streng, Middle Dutch strenge, Dutch streng, Old High German strang, German Strang "rope, cord"), from *strang- "taut, stiff," from PIE root *strenk- "tight, narrow." Gradually restricted by early Middle English to lines that are smaller than a rope. Sense of "a number of objects arranged in a line" first recorded late 15c.

Old English meaning "ligaments, tendons" is preserved in hamstring, heartstrings. Meaning "limitations, stipulations" (1888) is American English, probably from the common April Fool's joke of leaving a purse that appears to be full of money on the sidewalk, then tugging it away with an attached string when someone stoops to pick it up.

To pull strings "control the course of affairs" (1860) is from the notion of puppet theater. First string, second string, etc. in athletics (1863) is from archers' custom of carrying spare bowstrings in the event that one breaks. Strings "stringed instruments" is attested from mid-14c. String bean is from 1759; string bikini is from 1974.
tether (n.)youdaoicibaDictYouDict
late 14c., "rope for fastening an animal," not found in Old English, probably from a Scandinavian source akin to Old Norse tjoðr "tether," from Proto-Germanic *teudran (cognates: Danish tøir, Old Swedish tiuther, Swedish tjuder, Old Frisian tiader, Middle Dutch tuder, Dutch tuier "line, rope," Old High German zeotar "pole of a cart"), from PIE root *deu- "to fasten" + instrumentive suffix *-tro-. Figurative sense of "measure of one's limitations" is attested from 1570s.