borrowed from French acéto-, from Latin acētum "vinegar" + French -o- -o- — more at acetic acid
Note: The formative acéto- was apparently first used by the French chemist Claude Louis Berthollet in Éléments de l'art de la teinture (Paris, 1791), in the compound acide acéto-citrique, a name for a mixture of acetic acid and citric acid used for fixation in dyeing.