'softener' originates from the verb 'soften', which comes from the Old English word 'softian', where 'soft' meant 'gentle or mild'.

'softian' transformed into the Middle English word 'softnen', and eventually became the modern English word 'soften', from which 'softener' is derived.

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