'lympho-reactive' originates from the combining form 'lympho-' (from New Latin/Greek 'lymph', Latin 'lympha'), where 'lymph' meant 'clear fluid (lymph)', combined with English 'reactive' which ultimately derives from Latin elements 're-' + 'agere' meaning 'again' + 'to act'.

'lympho-reactive' was created in modern medical English by compounding the combining form 'lympho-' (formed from Latin 'lympha' via New Latin/Greek use) with the adjective 'reactive' (from the verb 'react'), becoming a specialized descriptive term in 20th-century biomedical literature.

Originally the elements referred simply to 'lymph (clear fluid)' and 'being reactive'; over time the compound has come to be used specifically for 'provoking or showing reactivity of lymphocytes (immune cells)' in immunology and pathology contexts.