As nouns the difference between hollowness and emptiness
is that hollowness is the state or quality of being hollow while emptiness is the state or feeling of being empty.
As a proper noun Emptiness is
a Chinese constellation near Aquarius and Equuleus, one of the 28 lunar mansions and part of the Black Turtle.
hollowness
English
Noun
(en-noun)
the state or quality of being hollow
emptiness
English
Noun
The state or feeling of being empty