'overindulge' originates from the prefix 'over-' meaning 'excessively' and the verb 'indulge' from Latin 'indulgere' meaning 'to be kind or lenient'.

'indulgere' transformed into the Old French word 'endulger' and eventually became the modern English word 'indulge'.

Initially, it meant 'to be kind or lenient', but over time it evolved into its current meaning of 'to allow oneself to have too much of something enjoyable'.