'lymphocyte-rich' originates from Modern English by combining the noun 'lymphocyte' and the adjective 'rich'. 'Lymphocyte' itself comes from New Latin 'lymphocytus' (or 'lymphocyte') derived from Greek elements where 'lympha' meant 'clear water, bodily fluid' and 'kytos' (via Latinized '-cytus/-cyte') meant 'cell'. 'Rich' originates from Old English 'rice' meaning 'wealthy, powerful' and later 'abundant'.

'lymphocyte' was coined in Neo-Latin/medical Latin in the late 19th century from Greek-derived elements and entered English medical usage; 'rich' comes from Old English 'rice' and Middle English 'rich'. The compound adjective 'lymphocyte-rich' is a Modern English formation (20th century onward) used in clinical and pathological descriptions to mean 'abundant in lymphocytes'.

Individually, 'lymphocyte' originally named a cell associated with 'lymph' (the clear bodily fluid) and 'rich' originally signified 'wealthy/powerful' or 'abundant'; combined in Modern English the phrase came to mean 'abundant in lymphocytes' with a specialized medical sense.