Etymology: < Middle French regement, régement, Middle French, French régiment, †regiment government, rule (1250 in Old French), (book of) rules for life or conduct (late 13th cent.), medical treatment, medical care (1314; 1272 as regimant ), control (c1384–5 in mettre en régement to subdue), direction, administration (1400–3), military unit under the command of a colonel (1553, after German Regiment (see below)), large number or people or things (1623) and its etymon post-classical Latin regimentum direction for government (4th cent.; recorded already in classical Latin in a grammarian of the 2nd cent. a.d. as a poetic alternative to regimen : see regimen n.), course of medical treatment (13th cent. in British sources) < classical Latin regere to rule (see regent adj.) + -mentum -ment suffix. Compare regimen n., regime n.Compare Old Occitan regimen administration, government, way of acting, conduct (both c1300), authority (14th cent.), Catalan regiment government, action of ruling (14th cent.), military unit under the command of a colonel, large number of people or things (both 19th cent.), Spanish regimiento way of ruling (1490), regime, regimen (c1495), military unit (1737 or earlier), Portuguese regimento rule, government (1361; later also in senses ‘conduct’ and ‘military unit’), Italian reggimento way of ruling or governing, action of ruling or governing (a1294; a1250 as regimento ), attitude, government, direction (a1321), administrative unit under the command of a colonel (1602), multitude (a1665). Compare also ( < French) Middle Dutch regement , Middle Dutch, Dutch regiment diet, prescription (1477), direction, influence (c1500), conduct, way of living (1510), government, rule (1527), system of government, political regime (1542), management, administration (1564), military unit (1566); ( < Latin) Middle Low German regiment , regimente , regement , etc. rule, act of governing, government, authority, order, group of people, military unit, etc., German Regiment rule, management, administration, authority (early 15th cent.), military unit under the command of a colonel (first half of the 16th cent.); (probably < Middle Low German) Old Swedish regiment , regement , Old Swedish, Swedish regemente government, authority, order, discipline (all early 16th cent.), military unit (1563), etc.; (probably reflecting forms in Latin, French, and German) Danish regimente (occasionally also regiment ) government, rule, way of life, order, discipline (formerly also †regement , †regemente ), regiment military unit (18th cent.; formerly also †regimente ). In the sense ‘military unit’ (compare sense 8) in most of the Romance and Germanic languages probably ultimately after German. A pronunciation with elision of the middle syllable is given as the primary one in D. Jones Eng. Pronouncing Dict. (1917) (remaining as an alternative in editions of Jones until 1988), is attested by the frequent spellings regment or reg'ment (from the late 16th cent. onwards), and is commented on already in the late 17th cent.:1674 E. Coles Compl. Eng. Schoolmaster 90/2 Read..redg-ment... Write..regiment.

Etymology: < regiment n.