'waterfowl-like' is a compound formed from the noun 'waterfowl' + the suffix '-like'. 'Waterfowl' itself combines 'water' and 'fowl', and the suffix '-like' comes from Old English '-lic' meaning 'having the body or nature of'.

'water' originates from Old English 'wæter'; 'fowl' from Old English 'fugol' (later Middle English 'foul'/'fowl'); the adjectival suffix '-like' comes via Middle English from Old English '-lic'. These elements combined in Modern English to form compounds such as 'waterfowl' and then descriptive compounds like 'waterfowl-like'.

Originally compounds like 'waterfowl' meant literally 'a fowl of the water'. Over time the productive suffix '-like' was used to form adjectives meaning 'resembling' or 'characteristic of', so 'waterfowl-like' came to mean 'having qualities of waterfowl' rather than indicating an actual species.