A certain archdeacon had a sumpnour, who acted as his secret spy, to bring before him all offenders. One day as he was riding forth on his business he met the devil disguised as a yeoman, swore eternal friendship, and promised to “go snacks” with him. They first met a carter whose cart stuck in the road, and he cried in his anger, “The devil take it, both horse and cart and hay!” Soon the horse drew it out of the slough, and the man cried, “God bless you, my brave boy!” “There,” said the devil, “is my own true brother, the churl spake one thing but he thought another.” They next came to an old screw, and the sumpnour declared he would squeeze twelve pence out of her for sin, “though of her he knew no wrong;” so he knocked at her door and summoned her “for cursing” to the archdeacon's court, but said he would overlook the matter for twelve pence, but she pleaded poverty and implored mercy. “The foul fiend fetch me if I excuse thee,” said the sumpnour, whereat the devil replied that he would fetch him that very night, and, seizing him round the body, made off with him. (Chaucer: Canterbury Tales.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894