'fact-checker' originates from Modern English, specifically formed from the compound 'fact-check' plus the agentive suffix '-er'. 'fact' ultimately comes from Latin 'factum' meaning 'deed' or 'thing done', and 'check' derives from Old French 'eschec' (related to chess) which developed senses related to stopping, testing, or verifying.

'fact-checker' developed in Modern English by adding the agent suffix '-er' to the verb compound 'fact-check' (a mid-to-late 20th century formation). The verb 'fact-check' itself was formed by combining the noun 'fact' and the verb 'check', and the noun 'fact-checker' named the person or entity performing that action.

Initially, 'fact-check' referred simply to the action of checking facts; over time the derived noun 'fact-checker' came to denote a dedicated person, organization, or tool whose role is to verify factual claims, especially in journalistic and digital contexts.