'appendant' originates from Latin, specifically the verb 'appendere', where the elements 'ad-' (to, toward) + 'pendere' (to hang) meant 'to hang upon'.

'appendant' passed via Medieval/ Late Latin (e.g. 'appendent-') and through Middle English formations to become the modern English adjective 'appendant'.

Initially it meant 'hanging upon, attached', and over time this developed into the current sense of 'attached or added to something' (including figurative senses like 'subordinate').