'eosinophil-rich' originates from the compound of 'eosinophil' (from New Latin/Greek: 'eosin' + Greek 'philos') and 'rich' (Old English 'rice'), where 'eosin' is ultimately from Greek 'ēōs' meaning 'dawn' (referring to the dawn-like red staining) and 'philos' meant 'loving', while 'rich' originally meant 'powerful' or 'wealthy'.

'eosinophil' developed in medical New Latin in the late 19th century (from 'eosin', the dye name, + '-phil'/'-philos'), and 'rich' evolved from Old English 'rice' to modern English 'rich'; the compound 'eosinophil-rich' is a modern English formation combining the established medical noun with the adjective 'rich'.

Initially, 'eosin' referred to the dye (from Greek 'dawn') and '-phil' referred to affinity for that dye; 'eosinophil' came to denote the specific white blood cell that stains with eosin. The compound 'eosinophil-rich' later came to mean 'abundant in eosinophils' in tissues or fluids.