'egoistic' originates from Latin, specifically the word 'ego', where 'ego' meant 'I', combined with the adjectival suffix '-istic' (from Greek '-istikos' via Latin/French) to form an adjective meaning 'relating to the ego or self-interest'.

'egoistic' developed in English from the noun 'ego' (Latin 'ego' = 'I') and from forms such as French 'égoïsme' / English 'egoism'; the adjective 'egoistic' was formed from 'egoism' + '-ic'/'-istic' in modern English usage.

Initially based on the Latin root meaning 'I', the term evolved through 'egoism' to denote a philosophical position emphasizing self-interest; it now commonly means 'self-centered' or 'motivated by self-interest'.