E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Koumiss or Kumiss.
Fermented mares milk used as a beverage by the Tartar tribes of Central Asia. A slightly alcoholic drink of a similar kind is made with great ceremony in Siberia. It consists of slightly sour cows milk, sugar, and yeast. (Russian, kumuisu.)
Kumiss is still prepared from mares milk by the Calmucks and Nogais, who, during the process of making it, keep the milk in constant agitation.Rawlinson: Herodotus, vol. iii. book iv. p. 2.
The ceremony of making it is described at full length by Noel, in the Dictionnaire de la Fable, vol. i. 833834.