'round-nosed' originates from Modern English as a compound of 'round' (meaning 'rounded' or 'circular') and 'nose' (meaning 'nose') with the adjectival suffix '-ed'.

'round' entered English via Middle English from Old French 'rond', ultimately from Latin 'rotundus'; 'nose' comes from Old English 'nosu'. The compound 'round-nosed' is therefore formed by combining these longstanding elements in English to describe a rounded nose.

Initially it simply described something that was 'round' in its nose area; over time the usage has remained essentially the same and continues to describe a blunt or rounded nose shape.