'phagocytic' originates from New Latin/Modern Latin and Greek, specifically from the Greek word 'phagein' where 'phagein' meant 'to eat' and from Greek 'kytos' (via New Latin forms) meaning 'container' or 'cell'; the adjective is formed from the noun 'phagocyte' plus the adjectival suffix '-ic'.

'phagocytic' changed from the New Latin/Modern Latin scientific formation based on Greek elements (coined in the late 19th century from 'phagocyte', itself formed from Greek 'phagein' + 'kytos') and entered English usage as the adjective 'phagocytic' in modern biological literature (term popularized after work by Élie/Il'ya Metchnikoff on phagocytosis around 1880s).

Initially it literally related to 'eating' (from Greek 'phagein' = 'to eat'), but over time it evolved into the specialized biological sense 'relating to the cellular engulfing and digestion of particles and microorganisms' used in modern science.