Where does “inefficacy” come from?

Inefficacy comes from Middle English in- combined with Latin efficacia (from efficax, meaning "effective"), ultimately deriving from Latin ex- and facio meaning "to do" or "to make."

inefficacy (English): The condition of being ineffective

Definitions

  1. The condition of being ineffective

Ancestry of “inefficacy”, step by step

StepLanguageWordMeaning
1EnglishefficacyAbility to produce a desired effect under ideal...
2Old Frenchefficace
3Latinefficaciaefficacy, effectiveness, efficiency; virtue;...
4Latinefficāxefficacious, effectual, powerful, efficient
5Latinefficiōto make out or work out; effect, execute, complete, accomplish, make, form, compose
6LatinexA name of the letter "X"; out of, from
7Latincommūnicōto impart, share
8Latincommūniscommon, commonplace, ordinary, general, universal, shared, shared alike, of both sides, belonging to two or more together
9Old Latincom(m)oinis
10Proto-Italickommoiniscommon
11Proto-Indo-Europeanḱom-moy-ni-held in common
12Proto-Indo-Europeanḱómbeside, near, by, with
13Proto-Indo-EuropeanḱeDeictic particle, here; Post-positional...
14Middle Englishkyt
15Russianкитwhale; genitive plural of ки́та
16Old Church Slavonicкитъwhale
17Ancient Greekκῆτοςwhale, sea monster; abyss
Every word from Ancient Greek κῆτοςEvery word from Old Church Slavonic китъEvery word from Russian кит