Where does “efficacious” come from?

Efficacious derives from Old French efficacieux, meaning effective or producing the desired result.

efficacious (English): Effective; possessing efficacy

Definitions

  1. Effective; possessing efficacy

Ancestry of “efficacious”, step by step

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

Words derived from “efficacious

Every word from Proto-Indo-European gʷet-
efficacious — Etymology, Origin & Word History | Etymology Explorer