'banditry' originates from Italian, specifically the word 'bandito', where 'bandire' meant 'to banish' (used of one proclaimed an outlaw).

'banditry' changed from Italian 'bandito' (past participle of 'bandire') and Old French 'bandit' and eventually became the modern English word 'banditry' via early modern borrowings into English.

Initially it was associated with the idea of being 'banished' or 'proclaimed an outlaw', but over time it evolved into the meaning 'acts of robbery and lawlessness by outlaws/bandits'.