English

inirritable

From in- + irritable.

Proto-Indo-European *h₁én ‘in’

Proto-Germanic *in ‘into’

English in-

Proto-Indo-European *h₃er- ‘to move, to stir’

…

Proto-Indo-European *h₃riH-tó-s ‘whirled, stirred’

Latin irrītō ‘to excite, to irritate’

Latin irritabilis ‘irritable, irascible, short-tempered’

French irritable

Today it means

adj Incapable of being stimulated into action, as a muscle.

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

Etymograph / inirritable