'arrogator' originates from Latin, specifically the verb 'arrogare', where the prefix 'ad-' (later assimilated as 'ar-') meant 'to' or 'toward' and 'rogare' meant 'to ask' or 'to propose'.

'arrogare' in Latin gave rise to Medieval Latin forms such as 'arrogator' (an agent noun meaning 'one who claims'), and from these Latin formations the English word 'arrogator' developed (via learned borrowing rather than direct Old English inheritance).

Initially, the root referred to 'asking for or claiming (by request or proposal)', and over time the sense shifted toward 'claiming or taking for oneself (often without right)', which is the core modern meaning.