'lymphoreactive' originates from Modern English, specifically formed from the combining form 'lympho-' (from Greek 'lymphē' meaning 'lymph') and the adjective 'reactive' (from Latin elements 're-' + 'agere' meaning 'to act').

'lympho-' derives from Greek 'lymphē' which entered Latin as 'lympha' and then into English as 'lymph'; 'reactive' comes from Latin 're-' + 'agere' via Late Latin/Medieval Latin into modern English 'reactive'. The compound 'lymphoreactive' is a 20th-century medical formation combining these elements.

Initially the roots separately referred to 'lymph' and 'reactive action'; combined as 'lymphoreactive' it came to mean specifically 'producing or showing a reaction in lymphatic/lymphoid tissue' in medical contexts.