'libidinous' originates from Latin, specifically the word 'libidinosus', where 'libido' meant 'desire' (often sexual).

'libidinous' developed from Latin 'libidinosus' into Late Latin and then entered English via Middle English (through learned borrowings), becoming the modern English word 'libidinous'.

Initially, it referred broadly to 'full of desire' (from 'desire'), but over time it narrowed to its current sense of 'having strong sexual desire; lustful.'