The name lactone derives from the ring compound called lactide, which is formed from the dehydration of 2-hydroxypropanoic acid (lactic acid) CH-CH(OH)-COOH. Lactic acid, in turn, derives its name from its original isolation from soured milk (Latin: lac, lactis). The name was coined in 1844 by the French chemist Théophile-Jules Pelouze, who first obtained it as a derivative of lactic acid. An internal dehydration reaction within the same molecule of lactic acid would have produced alpha-propiolactone, a lactone with a 3-membered ring.
In 1880 the German chemist Wilhelm Rudolph Fittig extended the name "lactone" to all intramolecular carboxylic esters.