Vowel

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Middle English: from Old French vouel, from Latin vocalis (littera) ‘vocal (letter)’.

wiktionary

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Borrowed into Middle English from Old French vouel (French voyelle), from Latin vōcālis(“voiced”), a semantic loan of Koine Greek φωνῆεν(phōnêen). Doublet of vocal.

etymonline

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vowel (n.)

c. 1300, from Old French voieul (Modern French voyelle), from Latin vocalis, in littera vocalis, literally "vocal letter," from vox (genitive vocis) "voice," from PIE root *wekw- "to speak." Vowel shift in reference to the pronunciation change between Middle and Modern English is attested from 1909. The English record-holder for most consecutive vowels in a word is queueing.