'arithmetician' originates from Middle French, specifically the word 'arithméticien', which was derived from Medieval Latin 'arithmeticianus', where 'arithmetica' meant 'arithmetic' and the suffix '-ianus' indicated a person related to a field.

'arithmeticianus' in Medieval Latin became 'arithméticien' in Middle French, and eventually became the modern English word 'arithmetician'.

Initially, it meant 'a person skilled in arithmetic', and this meaning has remained the same in modern usage.