changeling

nouns

a person of subnormal intelligence
changeling, cretin, half-wit, idiot, imbecile, moron, retard
a child secretly exchanged for another in infancy
changeling
is a type of (narrower)
a young person of either sex
"she writes books for children"; "they're just kids"; "`tiddler' is a British term for youngster"
child, fry, kid, minor, nestling, nipper, shaver, small fry, tiddler, tike, tyke, youngster