'inappetence' originates from Latin, specifically from the Late Latin/Medieval Latin word 'appetentia', where the root 'appetere' meant 'to seek after, desire', combined with the prefix 'in-' meaning 'not'.

'appetentia' (Late/Medieval Latin) gave rise to English 'appetence' (meaning desire), and the negative form 'inappetentia' or 'inappetence' developed to express lack of appetite; this evolved into the modern English 'inappetence'.

Initially connected to the broader sense of 'desire' or 'seeking', the compound came to be used specifically for 'lack of appetite', and in current usage it commonly denotes a medical/clinical loss of appetite.