'word-level' originates from Modern English as a compound of 'word' and 'level'. 'Word' ultimately comes from Old English 'word' (from Proto-Germanic *wurdą), where the root meant 'speech, utterance'; 'level' comes via Old French (e.g. 'livelle') from Late Latin 'libella', a diminutive of Latin 'libra' meaning 'balance, scale'.

'word' is attested in Old English as 'word' and continued through Middle English into Modern English unchanged in form; 'level' entered English from Old French/Medieval Latin and developed the sense 'flat, even' and then 'degree or rank'. The compound 'word-level' is a modern English formation (20th century onward) used in technical and analytical contexts.

Individually, 'word' originally meant 'speech' or 'utterance' and has remained close to 'word'; 'level' originally referred to a balance/flatness and broadened to mean 'degree or layer'. Combined, 'word-level' came to mean 'pertaining to the layer/degree of individual words' in analysis.