'anisocytosis' originates from Greek, specifically the elements 'anisos', 'kytos' and the suffix 'osis', where 'anisos' meant 'unequal', 'kytos' meant 'container, cell', and 'osis' meant 'condition or process'.

'anisocytosis' was formed in New Latin/medical terminology by combining Greek roots ('anisos-' + 'cyt-' + '-osis') and entered English usage in medical literature in the late 19th to early 20th century as a technical term for unequal cell size.

Initially, the components literally conveyed 'the condition of unequal cells'; over time it has retained this specialized clinical meaning referring specifically to unequal red blood cell sizes.