'atonement' originates from English (early Modern English), specifically formed from the phrase 'at one' + the noun-forming suffix '-ment', where 'at one' meant 'in agreement' or 'reconciled'.

'atonement' developed from Middle English forms such as 'at-ounement' or 'at oonement' and eventually became the modern English word 'atonement' meaning reconciliation or making amends.

Initially, it meant 'being at one' or 'unity/reconciliation'; over time it evolved into the current sense of 'the act of making amends or reparation for wrongdoing'.