'apposer' originates from French, specifically the word 'apposer', ultimately from Latin 'appōnere', where the prefix 'ad-' (assimilated to 'ap-') meant 'to/toward' and 'ponere' meant 'to place'.

'appōnere' in Latin developed into Old French forms such as 'aposer'/'apposer', and English borrowed the verb sense (appose) from French; the agent noun 'apposer' follows from this verbal base to denote 'one who apposes'.

Initially it meant 'to place upon or to put in position', and over time it has come to be used for 'placing side by side or in apposition' and as an agent noun meaning 'one who places or juxtaposes'.