IPA: /ɪˌrɛvəkəˈbɪlɪtɪ/
KK: /ɪˌrɛvəkəˈbɪlnəs/
The quality of being impossible to revoke or change; a state of being final and unchangeable.
The irrevocableness of her decision left no room for doubt or reconsideration.
Irrevocableness → It is formed from "in-" (meaning not), "revocare" (meaning to call back or revoke), and "-ness" (meaning the state of being). The word describes the state of being unable to be called back or revoked.
Think of 'not' ('in-') being able to 'call back' ('revocare') something, which is why 'irrevocableness' means it cannot be undone.