'lympho-inert' originates from Neo-Latin/modern scientific English, specifically composed from the combining form 'lympho-' (from Latin 'lympha') and the adjective 'inert' (from Latin 'iners'), where 'lympha' meant 'clear spring, lymph' and 'iners' meant 'inactive'.

'lympho-inert' changed from a Neo-Latin/medical compound formed by attaching the combining form 'lympho-' (derived via Latin 'lympha'/'lymph-') to the English adjective 'inert'; this coinage arose in modern medical/pathological usage and was adopted into English as the hyphenated term 'lympho-inert'.

Initially, it meant 'inactive or not related to lymph' in a combined-formation sense, but over time it evolved into the current specialized medical meaning of 'not provoking a lymphocytic (immune) reaction or infiltration'.