'tolerationist' originates from English, formed from 'toleration' + the agent suffix '-ist'; 'toleration' ultimately comes from Latin 'toleratio', from 'tolerare', where the root 'toler-' meant 'to bear' or 'to endure'.

'toleration' passed into Middle English from Old French (via Latin 'toleratio'), and the agent suffix '-ist' (from Greek/Latin via Old French) combined with it in Modern English to form 'tolerationist'.

Initially related to the idea of 'bearing' or 'endurance' (the act of tolerating), over time the meaning shifted toward advocacy: 'a person who supports allowing differing beliefs or practices', which is the modern sense of 'tolerationist'.