'coyness' ultimately derives from the adjective 'coy', which entered English from Old French 'coi' (also found in Anglo-Norman), where 'coi' meant 'quiet' or 'at rest'.

'coy' appeared in Middle English in forms such as 'coi' or 'quoy' (borrowed from Old French 'coi'), and over time the sense shifted from 'quiet, still' to 'bashful' or 'shy', giving rise to the noun 'coyness'.

Initially, it meant 'quiet' or 'at rest', but over time it evolved into the current sense of 'shyness or affected modesty' and sometimes 'evasive reserve'.