'improver' originates from the verb 'improve', which comes from the Latin word 'improbare', where 'in-' meant 'in' and 'probare' meant 'to test or prove'.

'improbare' transformed into the Old French word 'improver', and eventually became the modern English word 'improve', from which 'improver' is derived.

Initially, it meant 'to make better', and this meaning has largely remained the same in modern usage.