c. 1300, reine, "strap of a bridle," attached to it on either side of the head, by which the rider or driver restrains and guides the animal, from Old French rene, resne "reins, bridle strap, laces" (Modern French rêne), probably from Vulgar Latin *retina "a bond, check," a back-formation from Latin retinere "hold back" (see retain). Compare Latin retinaculum "a tether, halter, rein."
The figurative extension of reins to "guidance, means of controlling; control, check, restraint" is by mid-14c. Hence many expressions, originally from horse-management: Hold the reins "wield power" (early 15c.); take the reins "assume the power of guidance or government" (1610s). To give something free rein also is originally of horses; to give (a horse) the reins (1620s) is to allow it free motion.
also man-handle, mid-15c., "wield a tool," also, late 15c., "to attack (an enemy)," from man (n.) + handle (v.). Nautical meaning "to move by force of men" (without levers or tackle) is attested from 1834, and is the source of the slang meaning "to handle roughly" (1865). Related: Manhandled; manhandling.
[T]he two Canalers rushed into the uproar, and sought to drag their man out of it toward the forecastle. Others of the sailors joined with them in this attempt, and a twisted turmoil ensued; while standing out of harm's way, the valiant captain danced up and down with a whale-pike, calling upon his officers to manhandle that atrocious scoundrel, and smoke him along to the quarter-deck. [Melville, "The Town-Ho's Story," Harper's magazine, October 1851]
1560s, "to handle, train, or direct" (a horse), from the now-obsolete noun manage "the handling or training of a horse; horsemanship" (see manege, which is a modern revival of it), from Old French manège "horsemanship," from Italian maneggio, from maneggiare "to handle, touch," especially "to control a horse," which ultimately from Latin noun manus "hand" (from PIE root *man- (2) "hand").
Extended sense of "control or direct by administrative ability" any sort of business is by 1570s; meaning "to wield (a tool or object) by hand" is from 1580s. Meaning "effect by effort" (hence "succeed in accomplishing") is by 1732. Intransitive sense of "get by, carry on affairs" is suggested by 1650s, in frequent use from mid-19c. Related: Managed; managing. Managed economy was used by 1933.
Manage literally implies handling, and hence primarily belongs to smaller concerns, on which one may at all times keep his hand: as, to manage a house; to manage a theater. Its essential idea is that of constant attention to details: as, only a combination of great abilities with a genius for industry can manage the affairs of an empire. [Century Dictionary]