'asserter' originates from Latin, specifically the word 'assertor', where 'ad-' meant 'to' and 'serere' meant 'to join or put together'.

'asserter' changed from Old French or Medieval Latin forms such as 'assertor' and passed into Middle English (via words like 'asserten'/'assertour') and eventually became the modern English word 'asserter'.

Initially, it was connected to the idea of 'joining to' or 'attaching' (through Latin roots), but over time it evolved into the sense of 'affirming' or 'declaring something to be true'.