Etymology

From French acide propionique, coined by chemist Jean-Baptiste Dumas, from Ancient Greek πρῶτος ‎(prôtos) ("first") and πίων ‎(píōn) ("fat"), because it was the smallest carboxylic acid that exhibited the properties of the other fatty acids, such as producing an oily layer when salted out of water and having a soapy potassium salt.