'attingency' originates from Latin, specifically from a formation related to 'attingere' (to touch, to reach), with the noun-forming suffix '-ency' added in later English formation.

'attingency' changed from Middle English forms such as 'attingence' or 'attingency' (used for the act of reaching or attaining) and was preserved in later English as the rare noun 'attingency'.

Initially it meant 'the act of touching or reaching' (literal sense from Latin), but over time it evolved into the sense 'the act of attaining' or 'that which is attained' and is now rare or archaic.