'two-element' originates from Modern English as a compound of the numeral 'two' (from Old English 'twa') and the noun 'element' (from Latin 'elementum' via Old French and Middle English), where 'two' meant '2' and 'element' meant 'a fundamental constituent or part'.

'two' comes from Old English 'twa', while 'element' comes from Latin 'elementum' which entered English through Old French and Middle English as 'element'; the compound 'two-element' is a modern English formation combining these parts to describe something made of two elements.

Initially each component meant simply 'two' and 'a basic part' respectively; combined in Modern English the compound has retained the literal sense and is used adjectivally in technical contexts to mean 'consisting of two elements'.