'appetency' originates from Latin, specifically the word 'appetentia', where the root 'appetere' (from ad- + petere) meant 'to strive for' or 'to seek after'.

'appetency' changed from Middle English/Anglo-Norman 'appetence' (borrowed from Late Latin 'appetentia') and eventually became the modern English word 'appetency' (plural 'appetencies').

Initially it meant 'a striving or desire toward something,' and over time it evolved to the more general sense of 'a tendency, inclination, or appetite' as used today.