'irritable' originates from Latin, specifically the word 'irritabilis,' where 'irritare' meant 'to provoke or excite.'

'irritabilis' transformed into the Old French word 'irritable,' and eventually became the modern English word 'irritable' through Middle English.

Initially, it meant 'capable of being excited or stimulated,' but over time it evolved into its current meaning of 'easily annoyed or angered.'