'trumpet-like' is formed by combining the noun 'trumpet' and the adjective-forming suffix '-like', where '-like' meant 'similar to' or 'having the characteristics of'.

'trumpet' entered English from Anglo-Norman/Old French 'trompette' (a diminutive of 'trompe' meaning 'horn' or 'trumpet'), and the suffix '-like' derives from Old English '-līc' (Middle English '-like'); these combined in Modern English to form compounds such as 'trumpet-like' (also seen as 'trumpetlike').

Initially the components referred separately to the instrument 'trumpet' and the property 'like/similar to'; over time the compound has been used consistently to describe shapes or qualities resembling a trumpet and has retained that core sense.