(A ). A large Flemish gotch, i.e. a corpulent beer-jug of some strong ware, originally made in Flanders in ridicule of Cardinal Bellarmine, the great persecutor of the reformed party there. These jugs had at the neck a rude likeness of the cardinal with his large, square, ecclesiastical beard.
... like a larger jug, that some men call A bellarmine ... Whereon the lewder hand of pagan workmen, Over the proud ambitious head, hath carved An idol large, with beard episcopal, Making the vessel look like tyrant Eglon.
Cartright: The Ordinary.
“One of the Fellows of Exeter [College], when Dr. Prideaux was rector, sent his servitor, after nine o'clock at night, with a large bottle to fetch some ale from the alehouse. When he was coming home with it under his gown the proctor met him, and asked him what he did out so late, and what he had under his gown? The man answered that his master had sent him to the stationers to borrow Bellarmine, which book he had under his arm; and so he went home. Whence a bottle with a big belly is called a Bellarmine to this day, 1667.” —Oxoniana, vol. i. p. 232.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894