early 15c., "bodily fluid;" c. 1600 in specific sense of "mass of semi-liquid food in the stomach," from Late Latin chymus, from Greek khymos, nearly identical to khylos "juice" (see chyle) and meaning essentially the same thing; from PIE root *gheu- "to pour." Differentiated by Galen, who used khymos for "juice in its natural or raw state," and khylos for "juice produced by digestion," hence the modern distinction.