Koilia (G2836) is the word for the physical belly but carries far more theological weight in John 7:38 and 7:38: 'Whoever believes in me, as Scripture has said, rivers of living water will flow from within them [ek tes koilias].' The belly as the seat of deepest longing and outpouring is also found in Jesus weeping โ visceral, gut-level compassion.
John uses koilia to locate the wellspring of spiritual life in the deepest, most interior place โ not intellectual belief but a gut-level trust from which living water flows. Philippians 3:19 condemns those whose 'god is their belly [koilia]' โ where appetite rules supreme. The contrast is decisive: when the Spirit fills the koilia, living water flows out; when the flesh fills it, appetite devours.