Pertaining to, derived from, or designating, an organic
   acid which is produced in the distillation of wood, in the fermentation
   of various organic substances, as glycerin, calcium lactate, etc., and
   is obtained as a colorless liquid having a sharp, pungent odor.
   Propionic acid is so called because it is the first or lowest member of
   the fatty acid series whose salts have a fatty feel.