'fluid-depleted' is a compound formed from 'fluid' and 'depleted'. 'fluid' originates from Latin, specifically the word 'fluidus', related to 'fluere' meaning 'to flow'. 'depleted' originates from Latin 'deplēre' (via Old French and Middle English), where the prefix 'de-' had a sense of 'away/from' and 'plēre' (root of 'plenus') related to 'to fill'.

'fluid' entered English via Old French/Latin influence (Latin 'fluidus' → Old French/Medieval Latin forms → Middle English 'fluid'), while 'deplete' came from Latin 'deplēre' through Old French and Middle English as 'deplenish'/'deplete', with the past participle form 'depleted' becoming common in modern English. The compound 'fluid-depleted' is a modern English formation combining the noun and past-participle adjective.

Individually, 'fluid' originally meant 'flowing' and later 'a substance that flows', while 'deplete' originally meant 'to empty (out)'. Combined, the modern compound means 'having lost or been deprived of fluid', a sense used especially in medical and technical contexts.