The compound 'would-be' emerged in Middle English, directly combining the modal verb 'would', expressing conditional or desired action, with the infinitive 'be'. It initially appeared in phrases like "would be king" to denote someone who desired or claimed to be king. Over time, it grammaticalized into a fixed hyphenated adjective, shifting from a verbal phrase describing a wish to a pre-modifier labeling an aspirational but unfulfilled state. This evolution reflects a common pattern where a descriptive verbal construction becomes a lexicalized attribute, capturing the nuance of potentiality versus actuality.

Structure: would (modal verb) + be (verb) 'Would' originates from Old English 'wolde', the past tense of 'willan' (to wish, desire), of Germanic origin. 'Be' originates from Old English 'bēon', an irregular verb with multiple Germanic roots. In this compound, 'would' functions as a modal expressing intention or desire, and 'be' functions as the infinitive verb 'to be'.