'duck-billed' originates from English, specifically the combination of 'duck' + the past-participial adjective-forming 'billed', where 'duck' referred to the bird and 'bill' meant 'beak' or 'snout'.

'duck-billed' developed from the compound noun 'duck-bill' (used in the early 19th century to name animals like the platypus) and the adjectival use formed by adding the -ed participial/adjectival form to create 'duck-billed'.

Initially it literally meant 'having a bill like a duck'; over time the term retained that literal sense but was extended into taxonomic and descriptive names (e.g., 'duck-billed platypus', 'duck-billed dinosaur') and to describe objects resembling a duck's bill.