'barbarise' originates from Late Latin 'barbarizare', ultimately from Greek 'barbarizein', where 'barbar-' meant 'foreign, barbarian' and the suffix '-ize' (from Greek '-izein') meant 'to make or to render'.

'barbarizare' changed into Old French 'barbariser' and later entered English as 'barbarise' (via Middle English/French influence).

Initially it meant 'to behave like a barbarian' or 'to treat as a barbarian', but over time it came to mean more broadly 'to make barbarous; to brutalize or degrade'.