Where does “efficacy” come from?

Efficacy comes from Old French efficace, derived from Late Latin efficacia and Latin efficax, meaning "powerful" or "effectual," ultimately from Latin facio meaning "to do" with the prefix ex-.

efficacy (English): Ability to produce a desired effect under ideal...

Definitions

  1. Ability to produce a desired effect under ideal...

Ancestry of “efficacy”, step by step

StepLanguageWordMeaning
1Old Frenchefficace
2Latinefficaciaefficacy, effectiveness, efficiency; virtue;...
3Latinefficāxefficacious, effectual, powerful, efficient
4Latinefficiōto make out or work out; effect, execute, complete, accomplish, make, form, compose
5LatinexA name of the letter "X"; out of, from
6Latincommūnicōto impart, share
7Latincommūniscommon, commonplace, ordinary, general, universal, shared, shared alike, of both sides, belonging to two or more together
8Old Latincom(m)oinis
9Proto-Italickommoiniscommon
10Proto-Indo-Europeanḱom-moy-ni-held in common
11Proto-Indo-Europeanḱómbeside, near, by, with
12Proto-Indo-EuropeanḱeDeictic particle, here; Post-positional...
13Middle Englishkyt
14Germankittputty certain kinds of cement used for fixing e.g. window panes
15Old High Germankuti
16Proto-West Germanickwidugum, resin
17Proto-Germanickweduzresin

Words derived from “efficacy

Every word from Proto-Germanic kweduzEvery word from Proto-West Germanic kwiduEvery word from Old High German kuti