'wide-billed' originates from Modern English as a compound of 'wide' and 'bill', where 'wide' comes from Old English 'wīd' meaning 'broad' and 'bill' comes from Old English 'bile' meaning 'beak'.

'wide' continued from Old English 'wīd' into Middle English as 'wide', and 'bill' (meaning 'beak') comes from Old English 'bile' (with possible Norse influence); the compound form 'wide-billed' developed in post-medieval English as a descriptive compound and became the modern 'wide-billed'.

Initially formed simply to describe a 'wide' + 'bill' (beak), and over time it has retained that descriptive meaning of 'having a wide beak'.