In the article ‘embezzle’, the Etymonline dictionary states: ‘from Old French em- (see en- (1)) + besillier ’torment, destroy, gouge,‘ which is of unknown origin.’
However, in A.J. Greimas’ Dictionnaire de l’ancien français (published by Larousse), in the article ‘beser’ meaning ‘to frighten’, we find “besiller” with the meaning ‘to torment, mistreat’ which comes from the Germanic ‘bizen’ (to prick).
Here is a reproduction of the dictionary page: