'mourner' originates from Middle English, specifically the word 'mournour' (from the verb 'mournen'), where the suffix '-er' meant 'one who'.

'mourner' developed from the Middle English 'mournen'/'mournour', which in turn came from Old English 'murnan' (to mourn); the noun form was formed by adding the agentive suffix '-er'.

Initially, it meant 'one who laments or expresses sorrow'; over time this basic meaning has been retained, now commonly referring specifically to someone attending a funeral or grieving for the dead.