How to pronounce“bellying”in English

“Did it change into the cry of the wind, plaintive at first, angrily shrill as it freshened, rising to a tearing whistle, sinking to a musical trickle of air from the leech of the bellying sail?”

“1693, Simon de la Loubère, A New Historical Relation of the Kingdom of Siam, translated by A.P., London: Tho. Horne, Part II, Chapter II. Of the Houses of the Siamese, and of their Architecture in Publick Buildings, page 32, But the Principal Ornament of the Pagodes, is to be accompanied, as generally they are, with several Pyramids of Lime and Brick […] Some there are which diminish and grow thick again four or five times in their heighth, so that the Profile of them goes waving: But these Bellyings out are smaller as they are in a higher part of the Pyramid.”