English

inefficacy

From in- + efficacy.

A compound of in- + efficacy

Proto-Indo-European *h₁én ‘in’

Proto-Germanic *in ‘into’

English in-

Proto-Indo-European *dʰeh₁k-

…

Latin efficiō ‘to make out, work out’

Late Latin efficāx ‘efficacious’

Late Latin efficācia

Old French efficace

Today it means

noun The condition of being ineffective

Language periods are conventional ranges, not dates for this word.

Etymograph / inefficacy