"child" (of either gender or any age), "son or daughter," Old English bearn "child, son, descendant," from Proto-Germanic *barnan (source also of Old Saxon barn, Old Frisian bern, Old High German barn "child;" lost in modern German and Dutch), from PIE root *bher- (1) "to carry," also "to bear children."

Originally a general English word, in modern English restricted to northern England and Scottish from c. 1700. This was the English form of the original Germanic word for "child" (compare child). Dutch, Old High German kind, German Kind are from a prehistoric *gen-to-m "born," from the same root as Latin gignere (see genus and compare kind (n.)). Middle English had bairn-team "brood of children."

"chemical which occurs naturally in the brain and works like morphine," 1975, from French endorphine. First element from endogène "endogenous, growing within" (see endo- + genus); second element from morphine.