c. 1400, reguler, "member of a religious order bound by vows," from regular (adj.) and from Medieval Latin regularis "member of a religious or monastic order." Sense of "soldier of a standing army" is from 1756. Meaning "regular customer" is by 1852; meaning "leaded gasoline" is by 1978; regular (adj.) in the sense of "unleaded" is by 1974.
c. 1400, reguler, "belonging to or subject to a religious or monastic rule," from Old French reguler "ecclesiastical" (Modern French régulier) and directly from Late Latin regularis "containing rules for guidance," from Latin regula "rule, straight piece of wood" (from PIE root *reg- "move in a straight line"). The classical -a- was restored 16c.
In earliest use, the opposite of secular. Extended from late 16c. to shapes, verbs, etc., that followed predictable, proper, or uniform patterns. From 1590s as "marked or distinguished by steadiness or uniformity in action or practice;" hence, of persons, "pursuing a definite course, observing a universal principle in action or conduct" (c. 1600).
The sense of "normal, conformed or conforming to established customs" is from 1630s. The meaning "orderly, well-behaved" is from 1705. By 1756 as "recurring at repeated or fixed times," especially at short, uniform intervals. The military sense of "properly and permanently organized, constituting part of a standing army" is by 1706. The colloquial meaning "real, genuine, thorough" is from 1821.
Old English borrowed Latin regula and nativized it as regol "rule, regulation, canon, law, standard, pattern;" hence regolsticca "ruler" (instrument); regollic (adj.) "canonical, regular."
late 14c., "armed expedition," from Old French armée "armed troop, armed expedition" (14c.), from Medieval Latin armata "armed force," from Latin armata, fem. of armatus "armed, equipped, in arms," as a noun, "armed men, soldiers," past participle of armare "to arm," literally "act of arming," related to arma "tools, arms" (see arm (n.2)).
Originally used of expeditions on sea or land; restriction to "land force" is by late 18c. Transferred meaning "host, multitude" is c. 1500. Meaning "body of men trained and equipped for war" is from 1550s.
The Old English words were here (still preserved in derivatives such as harrier; see harry (v.)), from Proto-Germanic *harjan, from PIE *korio- "people, crowd;" and fierd, with an original sense of "expedition," from Proto-Germanic *farthi-, related to faran "travel" (see fare (v.)). In spite of etymology, in the Anglo-Saxon Chronicle here generally meant "invading Vikings" and fierd was used for the local militias raised to fight them. Army-ant is from 1863.
"one not belonging to a regular body" of any sort, "one not subject to or not conforming with established regulations," 1610s, from irregular (adj.). Main modern sense of "a soldier not of the regular army" is from 1747.
Doubtless, the life of an Irregular is hard; but the interests of the Greater Number require that it shall be hard. If a man with a triangular front and a polygonal back were allowed to exist and to propagate a still more Irregular posterity, what would become of the arts of life? Are the houses and doors and churches in Flatland to be altered in order to accommodate such monsters? [Edwin Abbot, "Flatland: A Romance of Many Dimensions," 1885]
1777, "soldier of the regular army of the rebelling British American colonies," from continental (adj.) in its specific sense. In the general sense "native or inhabitant of a continent" from 1828.
Also used of the paper money issued by the rebelling colonies, which, through its devaluation, led to the expression not worth a continental (which seems to be no earlier than 1851), sometimes not worth a continental dime.