'excluder' originates from Latin, specifically the word 'excludere', where the prefix 'ex-' meant 'out' and 'cludere' (from 'claudere') meant 'to shut'.

'excludere' passed into Late Latin and Old French forms (e.g. 'esclure'/'exclure') and into Middle English as 'exclude', with the agentive suffix '-er' later forming 'excluder' in Modern English.

Initially it meant 'to shut out' or 'to shut away', and over time it evolved into the current sense of 'to keep out; to prevent inclusion' and thus 'excluder' as 'one who or that which excludes'.