'seaport' originates from Modern English as a compound of two older English words: 'sea' and 'port', where 'sea' comes from Old English 'sǣ' meaning 'sea' and 'port' ultimately comes from Latin 'portus' meaning 'harbor' via Old French/Old English.

'seaport' developed as a straightforward compound in English (Modern English 'seaport') from the combination of the native English element 'sea' (Old English 'sǣ') and the loanword 'port' (from Latin 'portus' through Old French and Middle English), becoming the modern English word 'seaport'.

Initially the components simply meant 'sea' and 'harbor', and over time the compound came to mean specifically 'a harbor on the sea' or 'a town with such a harbor'—the basic meaning has remained stable.