Do you know ghouls from goblins and ghosts?
late 14c., "bird too young to leave the nest," from nest (n.) + diminutive suffix -ling.
Old English nestlian "build a nest," from nest (see nest (n.)). Figurative sense of "settle (oneself) comfortably, snuggle" is first recorded 1540s. Related: Nestled; nestling.