'assoilment' originates from Middle English, ultimately from Old French/Anglo-Norman elements related to a verb meaning 'to release' and is derived from Latin 'solvere' meaning 'to loosen, release'.

'assoilment' appeared in Middle English as forms such as 'assoylment' or 'assoilment', influenced by Old French verbal forms related to Latin 'solvere'; over time the form stabilized as the English noun 'assoilment' (now archaic).

Initially it meant 'the act of freeing or releasing (someone)', and over time it retained this basic sense but became specialized and archaic, typically referring to acquittal or absolution.