'archsewer' originates from a compound of the prefix 'arch-' (ultimately from Greek 'arkhos' meaning 'chief', via Latin/Old French influence) and the Old French word 'asseour' (from 'asseoir' meaning 'to seat'), where 'arch-' meant 'chief' and 'asseour' meant 'one who seats (guests)'.

'archsewer' changed from Middle English compound forms such as 'archesewer' or 'archessewer'; the element 'sewer' itself comes from Old French 'asseour' (from 'asseoir'), and these parts combined in English to form the modern (now archaic) word 'archsewer'.

Initially, it meant 'the chief of the sewers, the principal officer in charge of seating and serving at table.' Over time the term retained this narrow, specialized sense and became archaic, now used mainly in historical contexts.