'appendency' originates from Medieval Latin, specifically the word 'appendentia', where 'ad-' (or assimilated 'ap-') meant 'to' and 'pendere' meant 'to hang'.

'appendency' changed from the Medieval Latin word 'appendentia' into Middle English forms such as 'appendence' and eventually became the modern English word 'appendency'.

Initially, it referred literally to 'the act or state of hanging on' (i.e., being attached), and over time it evolved into the more general sense of 'being appended or an appended thing'.