Belly - Vine's Expository Dictionary of New Testament Words
Belly[ 1,,G2836, koilia ]
from koilos, hollow" (Lat., coelum, "heaven," is connected), denotes the entire physical cavity, but most frequently was used to denote "the womb." In John 7:38 it stands metaphorically for the innermost part of man, the soul, the heart. See WOMB.
[ 2,,G1064, gaster ]
(cp. Eng., "gastritis"), is used much as No. 1, but in Titus 1:12, by synecdoche (a figure of speech in which the part is put for the whole, or vice versa), it is used to denote "gluttons," RV, for AV, "bellies." See GLUTTON, WOMB.