'antiegoistic' originates from the prefix 'anti-' (from Greek 'anti' meaning 'against') combined with 'egoistic' (from Latin 'ego' meaning 'I' with the adjectival suffix '-istic').

'antiegoistic' was formed in modern English by attaching the earlier adjective 'egoistic' to the productive prefix 'anti-' to yield a word meaning 'against egoism'; the elements trace back through Late Latin and Greek roots.

Initially it expressed the literal formation 'against egoism'; over time it has been used as an adjective describing attitudes, actions, or philosophies that oppose self-centeredness and promote others' interests.