'westernise' originates from English, formed from 'western' (relating to the west) plus the verb-forming suffix '-ise' / '-ize', where the suffix meant 'to make or become'.

'western' developed from Old English 'west' with the adjectival suffix '-ern'; the verb-forming suffix '-ize/-ise' comes via Old French and Latin/Greek formation patterns, producing 'westernise' in Modern English.

Initially related to 'western' meaning 'of the west (direction or region)'; over time the verb came to mean 'to make something adopt Western characteristics' rather than merely indicating geographic direction.