late 14c., "making, producing immediate effect, active, effective," from Old French efficient and directly from Latin efficientem (nominative efficiens) "effective, efficient, producing, active," present participle of efficere "work out, accomplish," from assimilated form of ex "out" (see ex-) + facere "to do" (from PIE root *dhe- "to set, put"). Meaning "productive, skilled" is from 1787. Related: Efficiently.

1590s, "power to accomplish something," from Latin efficientia "efficient power; efficiency; influence" (from efficientem; see efficient) + -cy. In mechanics, "ratio of useful work done to energy expended," from 1858. Attested by 1951 as short for efficiency apartment (itself from 1917).

also co-efficient, c. 1600, "that which unites in action with something else to produce a given effect," from co- + efficient. Probably influenced by Modern Latin coefficiens, which was used in mathematics in 16c., introduced by French mathematician François Viète (1540-1603). As an adjective, "acting in union to the same end," from 1660s. Related: Coefficiency.

1748, "not producing or incapable of producing the desired effect," from in- (1) "not, opposite of" + efficient. Related: Inefficiently.

*dhē-, Proto-Indo-European root meaning "to set, put."

It forms all or part of: abdomen; abscond; affair; affect (v.1) "make a mental impression on;" affect (v.2) "make a pretense of;" affection; amplify; anathema; antithesis; apothecary; artifact; artifice; beatific; benefice; beneficence; beneficial; benefit; bibliothec; bodega; boutique; certify; chafe; chauffeur; comfit; condiment; confection; confetti; counterfeit; deed; deem; deface; defeasance; defeat; defect; deficient; difficulty; dignify; discomfit; do (v.); doom; -dom; duma; edifice; edify; efface; effect; efficacious; efficient; epithet; facade; face; facet; facial; -facient; facile; facilitate; facsimile; fact; faction (n.1) "political party;" -faction; factitious; factitive; factor; factory; factotum; faculty; fashion; feasible; feat; feature; feckless; fetish; -fic; fordo; forfeit; -fy; gratify; hacienda; hypothecate; hypothesis; incondite; indeed; infect; justify; malefactor; malfeasance; manufacture; metathesis; misfeasance; modify; mollify; multifarious; notify; nullify; office; officinal; omnifarious; orifice; parenthesis; perfect; petrify; pluperfect; pontifex; prefect; prima facie; proficient; profit; prosthesis; prothesis; purdah; putrefy; qualify; rarefy; recondite; rectify; refectory; sacrifice; salmagundi; samadhi; satisfy; sconce; suffice; sufficient; surface; surfeit; synthesis; tay; ticking (n.); theco-; thematic; theme; thesis; verify.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dadhati "puts, places;" Avestan dadaiti "he puts;" Old Persian ada "he made;" Hittite dai- "to place;" Greek tithenai "to put, set, place;" Latin facere "to make, do; perform; bring about;" Lithuanian dėti "to put;" Polish dziać się "to be happening;" Russian delat' "to do;" Old High German tuon, German tun, Old English don "to do."

"quality of being effectual, producing the desired effect," 1520s, from Latin efficacia "efficacy, efficiency," from efficax (genitive efficacis) "powerful, effectual, efficient," from stem of efficere "work out, accomplish" (see effect (n.)).

Earlier in English in the same sense was efficace (c. 1200), from Old French eficace (14c.), from Latin efficacia; also efficacite (early 15c.), from Latin efficacitatem.

"efficient, no-nonsense," 1739, from workman + like (adj.).

tropical American plant, also its root used as a medicinal preparation, 1570s, from Spanish zarzaparrilla, from zarza "bramble" (from Arabic sharas "thorny plant" or Basque sartzia "bramble") + parrilla, diminutive of parra "vine," which is of unknown origin.

In 16c.-17c. the dried roots were held to be efficient in treatment of syphilis. From mid-19c. applied to a sweet soft drink made with the root extract (originally with suggestion of medicinal benefit).

1610s, "one who or that which rips," in any sense of that word, originally chiefly in technical use and slang, agent noun from rip (v.).

The meaning "killer who mutilates his victims" (1890) is from Jack the Ripper, the notorious London serial murderer of 1888-1891, whose nickname contains a pun on ripper in sense of "tool for ripping" old slates, etc. (1823) and the slang meaning "very efficient or excellent person or thing, a 'ripping' fellow" (1838), from ripping (q.v.) in the sense of "excellent, splendid."

"sure to have the desired effect" (often of medicines), 1520s, from Latin efficaci-, stem of efficax "powerful, effectual, efficient," from stem of efficere "work out, accomplish" (see effect (n.)) + -ous. Related: Efficaciously; efficaciousness.