'non-excitable' is formed from the prefix 'non-' (from Latin 'non', meaning 'not') combined with 'excitable', which derives from Latin 'excitare' meaning 'to rouse' or 'to call forth'.

'excitable' comes from Latin 'excitare' → Late Latin/Vulgar Latin forms → Old French/Anglo-Norman influences (e.g. 'exciter') → Middle English forms 'exciten'/'excite' and the adjective 'excitable'; the modern compound 'non-excitable' is a negated adjective formed by adding 'non-' to 'excitable'.

Originally 'excitable' meant 'able to be roused or stirred'; in the compound 'non-excitable' the meaning is the direct negation: 'not able or prone to being roused', i.e., 'not easily excited'.