'two-word' originates from Old English elements: 'twā' (two) and 'word' (word), where 'twā' meant 'two' and 'word' meant 'word'.

'Two' derives from Old English 'twā' and Proto-Germanic '*twai-/*twō', while 'word' comes from Old English 'word' (from Proto-Germanic '*wurdan'). The compound form (numeral + noun, often hyphenated) is a feature of modern English usage that developed by straightforward combination of these elements.

Initially a literal combination meaning 'two' + 'word' (i.e., 'consisting of two words'); the meaning has remained essentially the same in modern usage.