the squire of Don Quixote, was governor of Barataria, according to Cervantes. He is described as a short, pot-bellied rustic, full of common sense, but without a grain of “spirituality.” He rode upon an ass, Dapple, and was famous for his proverbs. Panza, in Spanish, means paunch.
A Sancho Panza. A justice of the peace. In allusion to Sancho, as judge in the isle of Barataria. Sancho Panza's wife, called Terea, pt. ii. i. 5; Maria, pt. ii. iv. 7; Juaa, pt. i. 7; and Joan, pt. i. 21. Sancho. The model painting of this squire is Leslie's Sancho and the Duchess.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894