'acari' originates from Greek, specifically the word 'akari', where 'a-' meant 'not' and 'kari' meant 'head', referring to the small size and headless appearance of mites and ticks.

'akari' transformed into the Latin word 'acarus', and eventually became the modern English word 'acari'.

Initially, it referred to 'small creatures without a distinct head', and this meaning has largely remained the same in modern usage.