Hollow
Old English holh ‘cave’; obscurely related to hole.
wiktionary
From Middle English holow, holowe, holwe, holwȝ, holgh, from Old English holh(“a hollow”), from Proto-Germanic *halhwaz, from Proto-Indo-European*ḱelḱwos. Cognate with Old High German huliwa and hulwa, Middle High German hülwe. Perhaps related to hole.
From Middle English holowe, holwe, holuȝ, holgh, from the noun (see above).
Compare holler.
etymonline
hollow (adj.)
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.
hollow (v.)
late 14c., "to make hollow," holowen, from hollow (adj.). Related: Hollowed; hollowing. Old English had holian "to hollow out."
hollow (n.)
"lowland, valley, basin," 1550s, probably a modern formation from hollow (adj.), which is from Old English holh (n.) "cave, den; internal cavity."
