'seawater-precipitated' is a modern English compound formed from 'seawater' (Modern English) + the past participle 'precipitated' (from the verb 'precipitate'). 'Seawater' itself is built from 'sea' (Old English 'sǣ') + 'water' (Old English 'wæter'). 'Precipitated' comes ultimately from Latin 'praecipitatus' (past participle of 'praecipitare'), via Late Latin/Medieval Latin and adoption into Modern English.

'sea' came from Old English 'sǣ' and 'water' from Old English 'wæter'; 'precipitate' entered English from Medieval/Modern Latin 'praecipitare' (through French/Latin-mediated forms), giving English 'precipitate' and the past participle 'precipitated'. These elements were compounded in modern technical usage to form 'seawater-precipitated'.

Each element retained its original sense ('sea' and 'water' denoting the ocean and its water; 'precipitated' meaning 'caused to settle out'). Combined in scientific contexts, the compound came to specifically mean 'having been deposited by precipitation from seawater' rather than more general senses of 'precipitated'.