ireful comes from ire (from Old French ire, from Latin ira 'anger') plus the suffix -ful 'full of'. Morphologically, the ending is part of the etymology: the suffix is attached to the older base named in the history, producing a later English derivative. In present English, the adjective sense is "full of anger; wrathful", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as ire, irate, and irascible, and in derivatives such as irefully and irefulness. Its semantic neighborhood includes angry, wrathful, furious, and irate, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Latin ira.