'arithmetize' originates from Greek 'arithmos', where 'arithmos' meant 'number', combined with the suffix '-ize' (from Greek '-izein' via Latin '-izare' and Old French '-iser') meaning 'to make or to render'.

'arithmetize' was formed in Modern English by adding the productive verb-forming suffix '-ize' to 'arithmetic' (which itself comes from Old French 'arithmetique', Latin 'arithmetica', ultimately from Greek 'arithmetike'), yielding the verb meaning 'to make or treat by arithmetic'.

Initially it meant 'to apply arithmetic or perform arithmetic on', and over time it has come to be used more generally as 'to express or reduce to numerical terms; to quantify'.