'annualize' originates from Latin, specifically the word 'annus' (meaning 'year'), combined with the verb-forming suffix '-ize' (from Greek '-izein' via Late Latin), creating a verb meaning 'make or express as yearly'.

'annualize' developed in English by adding the productive suffix '-ize' to the adjective 'annual' (from Latin 'annalis', from 'annus'), yielding the verb 'annualize' which later produced forms like 'annualized'.

Initially, it meant 'to make yearly' or 'to make into an annual form'; over time it took on the specialized sense 'to convert a figure into an annual rate' (commonly used in finance and statistics).