compliment

Compliment and complement, so often confused, are in effect doublets. They come from the same ultimate source, Latin complēmentum, a noun derived from complēre ‘fill up, finish’ (source of English complete and accomplish). English borrowed complement direct from Latin in the 14th century in the sense ‘fulfilment, accomplishment’, and by the 16th century this had developed the more specific metaphorical meaning ‘fulfilment of the obligation of politeness’ – hence ‘polite words of praise’. But then in the 17th century came competition in the form of compliment, also meaning ‘polite words of praise’. This also came from Latin complēmentum, but along a circuitous route via vulgar Latin *complimentum, Spanish cumplimiento, and French compliment. It gradually took over from complement in this ‘flattering’ sense, while complement went on to develop its leading current meaning, ‘counterpart’, in the 19th century.