means Having an empty space inside, rather than being solid all the way through; also used of sounds that echo with that emptiness, or feelings that ring false and unsatisfying.

from From Old English 'holh,' meaning a hollow place or hole, related to 'hol' (hole) and to broader Germanic words for cavities and concavities. The kinship is old and deep: a hollow was first a dip in the land, a hole in the ground, before the word stretched to describe anything scooped out, empty within, or — by a fitting leap — empty in spirit.