'nineteen-twenties' is formed in Modern English from the numerals 'nineteen' and 'twenty' with a plural suffix; 'nineteen' ultimately comes from Old English 'nigontiene' (where elements meant 'nine' and 'ten'), and 'twenty' comes from Old English 'twentig' (where 'twe-' meant 'two' and '-tig' meant 'group of ten').

'nineteen' changed from Old English 'nigontiene' to Middle English forms and then to modern 'nineteen'; 'twenty' changed from Old English 'twentig' through Middle English 'twentie' to modern 'twenty'; the compound expression for decades (e.g. 'the nineteen-twenties') developed in modern English usage to label the decade 1920–1929.

Initially these were simple numeric compounds naming numbers; over time the compound came to be used as a decade label and then as a cultural-era label (e.g. 'the nineteen-twenties' implying the social and cultural features of the 1920s).