c. 1200, adjective developed from Old English holh (n.) "hollow place, hole," from Proto-Germanic *hul-, from PIE root *kel- (1) "to cover, conceal, save." The figurative sense of "insincere" is attested from 1520s. Related: Hollowly. Spelling development followed that of fallow, sallow. Adverbial use in carry it hollow "take it completely" is first recorded 1660s, of unknown origin or connection. Hollow-eyed "having deep, sunken eyes" is attested from 1520s.
late 14c., "to make hollow," holowen, from hollow (adj.). Related: Hollowed; hollowing. Old English had holian "to hollow out."
"lowland, valley, basin," 1550s, probably a modern formation from hollow (adj.), which is from Old English holh (n.) "cave, den; internal cavity."