Etymology: < Anglo-Norman raigne, raine, rein, reine, reisne, ren, reyn, reyne, Anglo-Norman and Old French, Middle French resne, Anglo-Norman and Middle French rene, Old French reigne, Old French, Middle French regne, Middle French rayne, renge (French rêne , †resne ; in Anglo-Norman and Old French also as redne (mid 12th cent.)) long narrow strap used to control and guide a horse or other animal (c1100), control, capacity to direct or govern (c1240 in les resnes d'un pays (plural)), means of guiding or controlling, curb, restraint (1268 or earlier in Anglo-Norman in laisser trop longe reisne to give too much leeway to) < post-classical Latin retina rein (8th cent.; etymologically distinct from retina retina n.¹) < classical Latin retinēre retain v. (compare classical Latin retināculum retinaculum n.). Compare Old Occitan regna (c1200; late 12th cent. as renna), Catalan regna (1170), Portuguese redea (1364; 13th cent. as redeẽa), Italian redina (a1290 in plurals redine and †retene; chiefly in plural), and (apparently with elision of unstressed vowel and metathesis of consonants) Spanish rienda (a1207). Compare also post-classical Latin reina, reinum (from 13th cent. in British sources; probably < French).The following could show an earlier example of sense 1a(b), but more probably shows an example of the Anglo-Norman word:1340 in F. R. Chapman Sacrist Rolls Ely (1907) II. 92 In j par de reynes pro frenis palefredi. It is unclear whether the -s- in medieval French forms with -sn- reflects assimilation of *-tn- (which resulted from the regular loss of the unstressed -i- in the post-classical Latin etymon) or is purely graphic. Post-classical Latin retina superseded classical Latin habēna habena n.; it has been suggested that this was due to homonymic clash with the reflex of classical Latin avēna oats (see aveyn n.), which would have occurred frequently in a farming context, although this is far from certain. In the reins of government at sense 2b perhaps after French les rênes du gouvernement (1601 or earlier as †les resnes du gouvernement).

Etymology: < forms in one or more Scandinavian languages: compare early modern Danish ren , rin (Danish ren , †reen ), Norwegian ren , rein , Old Swedish ren (Swedish ren , †reen , †renn , †rhen ), all cognate with Old Icelandic hreinn , of uncertain origin, perhaps ultimately < the same Indo-European base as ancient Greek κριός ram (see crio- comb. form); if so, the animal may have been given its name on account of its antlers or ‘horns’ (with this semantic motivation, compare hart n., and also German Rind : see rother n.). Compare earlier reindeer n.The Scandinavian word was also borrowed into other European languages. Compare e.g. early modern Dutch reen (1595; also reyn), early modern German rein (1563; German Ren; compare also the synonymous early modern German rainer, reiner, reinger, reyner (1563), the morphological structure of which is unclear), Middle French reen (1552 in a translation from German of S. Münster Cosmographia; French renne (1678)), and (via French) Italian renna (1745; 1679 as †renne, masculine noun; a1557 in a journal of a voyage to Muscovy as †reno, (plural) †rheni). N.E.D. (1906) gives the pronunciation as (rēⁱn) /reɪn/.

Etymology: < rein n.¹ Compare Anglo-Norman (rare) raigner to rein (a horse) in (c1185 or earlier in an apparently isolated attestation; compare French rêner (late 19th cent.)).