'irritant' originates from Latin, specifically the word 'irritare,' where 'ir-' meant 'in' and 'ritare' meant 'to excite or provoke.'

'irritare' transformed into the French word 'irritant,' and eventually became the modern English word 'irritant' through Middle English.

Initially, it meant 'to provoke or excite,' but over time it evolved into its current meaning of 'causing discomfort or inflammation.'