'experimenter' originates from English, specifically the word 'experiment' with the agent-forming suffix '-er' to denote 'one who performs an experiment'.

'experiment' derives from Latin 'experimentum' (from 'experiri', meaning 'to try') via Old French 'esperiment' and Middle English 'experiment'; the modern English agent noun 'experimenter' was formed by adding '-er' to 'experiment'.

Initially, 'experiment' meant 'a trial or test'; with the addition of the suffix '-er' it came to mean 'one who carries out trials,' and the sense broadened to include people who try new methods or approaches.