the word is a modern english compound, formed by combining the noun 'veto' with the adjective-forming suffix '-proof'. the latin root 'veto' was a first-person singular verb meaning "i forbid," used in ancient rome by tribunes to block senatorial decrees. the element '-proof' evolved from the old english and latin verbs for testing and proving, developing a sense of being able to withstand a test or assault, as seen in words like 'waterproof' or 'fireproof'. when combined, the literal construction "forbid-resistant" logically yields the contemporary political meaning of being immune to the act of forbidding or rejecting, typically by an executive authority.

Structure: veto + proof - veto: from latin 'veto', meaning "i forbid". it functions as a noun used attributively to modify the second element. - proof: from old english 'prōfian' (to test) and latin 'probāre' (to prove, test). it functions as a combining form meaning "resistant, immune, impervious to".