'expropriator' originates from Latin, specifically from the verb 'expropriare' (and past participle 'expropriatus'), where the prefix 'ex-' meant 'out of' and 'proprius' meant 'one's own'.

'expropriator' developed through Late Latin forms (e.g. 'expropriatus') and via Medieval/early modern Latin and French derivatives into the English verb 'expropriate' (early 17th century); the agent noun 'expropriator' was later formed in English from that verb.

Initially related to the idea of taking away or depriving ownership ('making not one's own'), it evolved into the current sense of officially taking private property (often by the state) for public purposes, typically with compensation.