'banditism' originates from Italian/French, specifically the word 'bandito' (Italian) and 'bandit' (French/English), where 'bandire' (It.) meant 'to proclaim as outlaw/banish'; the English noun was formed by adding the suffix '-ism' (from Greek/Latin) meaning 'practice or system'.

'bandit' came into English via French from Italian 'bandito' (past participle of 'bandire'), and later the English formation 'bandit' combined with the suffix '-ism' produced 'banditism' to denote the practice or condition associated with bandits.

Initially the root conveyed the idea of being 'banished' or 'declared an outlaw'; over time the sense shifted to refer specifically to the activities of brigands and, by extension, the social phenomenon of bandits—hence the modern meaning 'the practice or condition of banditry'.