Italian 'sì', Spanish 'sí' and many more Romance words for "yes" come from Latin 'sīc' (so; like that).
French 'oui' doesn't. It comes from Old French 'oïl', a univerbation of 'o il', literally "yes, it (is/does/has etc.)".
'O' stemmed from Latin 'hoc' (this), which in Occitan became 'òc' (yes):
French 'oui' doesn't. It comes from Old French 'oïl', a univerbation of 'o il', literally "yes, it (is/does/has etc.)".
'O' stemmed from Latin 'hoc' (this), which in Occitan became 'òc' (yes):
Comments
Yes this etymology makes sense. Thanks, Yoïn.