'vowel' originates from Latin, specifically the word 'vocalis', where 'voc-' (from 'vox') meant 'voice'.

'vocalis' passed into Old French as 'vouel' (or similar forms) and then into Middle English as 'vowel', becoming the modern English word 'vowel'.

Initially related generally to 'vocal' or 'of the voice', the meaning narrowed to denote the specific class of speech sounds (and the letters representing them) used in pronunciation.