irritable

The word 'irritable' has a direct lineage from Latin, entering English in the mid-17th century. It is built upon the verb root irrit-, from irritare, which carried the core sense of provoking excitement or annoyance. The adjectival suffix -able was then attached, shifting the meaning from the action of provoking to the passive state of being "capable of being provoked." This etymological logic perfectly maps to the modern definition: having a nature that is easily excited to anger or annoyance. In scientific contexts, this concept was extended to describe tissues or organs that are easily excited or react to minor stimuli.

Structure: irrit (provoke) + able (capable of) irrit: From Latin irritare meaning 'to excite, provoke, annoy'. Its functional role is the core verb root. able: From Latin -abilis, a suffix forming adjectives meaning 'capable of, fit for, tending to'. Its functional role is an adjectival suffix.