'fluid-replete' is a compound of 'fluid' and 'replete.' 'fluid' originates from Latin, specifically the word 'fluidus,' where 'flu-'/'fluo' meant 'to flow.' 'replete' originates from Latin, specifically the word 'repletus,' from 'replēre' where 're-' meant 'again/together' and 'plēre' meant 'to fill.'

'fluid' passed into English via Latin 'fluidus' (and Old French influences) to Middle English 'fluid'; 'replete' came from Latin 'repletus' through Middle English and Anglo-Norman into Modern English; the compound 'fluid-replete' is a modern English formation combining these two elements as an adjective.

Individually, 'fluid' originally emphasized 'flowing' and 'replete' meant 'filled.' Combined, the phrase evolved to mean specifically 'filled with fluid' (the component meanings remain but together specify the type of filling).