'unfamiliarize' originates from the prefix 'un-' meaning 'not' and the word 'familiarize' which comes from 'familiar', derived from Latin 'familiaris' meaning 'of a household, domestic'.

'familiarize' transformed from the Latin word 'familiaris' and eventually became the modern English word 'familiarize', with 'un-' added to form 'unfamiliarize'.

Initially, it meant 'to make something not familiar', and this meaning has largely remained the same in modern usage.