Green’s Dictionary of Slang

elly-bay n.

the belly.

1938		D. Runyon ‘The Big Umbrella’ in Runyon on Broadway (1954) 563: ‘Downstairs, Jonas,’ I say. ‘In the elly-bay, Jonas.’.
1943		R.L. Bellem ‘Feature Snatch!’ Dan Turner - Hollywood Detective Feb. 🌐 An ugly sensation slugged me in the pit of the elly-bay with the force of a battering ram.
1945		R.L. Bellem ‘Dead Don’t Dream’ in Hollywood Detective July 🌐 His elly-bay shook as he laughed at his own corny jape.