speckle-belly, n. — Green’s Dictionary of Slang

speckle-belly n.

[? a distinctive style of garment, presumably a waistcoat, sported by such figures, but note also northeastern US dial. speckle-belly, a grey duck. Nonconformist clergymen were more likely to dress in muted than colourful tones]

(US) a dissenter, a nonconformist.

1873

Sl. Dict. 303: Specklebellies, Dissenters. A term used in Worcester and the North, though the etymology seems unknown in either place.