'seabed' originates from Old English, specifically the words 'sǣ' meaning 'sea' and 'bed' meaning 'bottom or floor'.

'sǣ' and 'bed' combined in Old English to form 'sǣbed', which evolved into the modern English word 'seabed'.

Initially, it meant 'the bottom of the sea', and this meaning has largely remained the same in modern usage.