Perhaps suggested by a line in Butler's poem, "On Critics": "As butchers are forbid to b'of a jury." See The Poetical Works of Samuel Butler, ed. Reginald Brimley Johnson, (London: George Ball & Sons,1851), Vol. II, p. 174. On whether butchers were actually excluded from juries, see Notes and Queries, no. 82 (May 24, 1851), p. 408.https://en.wikiquote.org/wiki/Butchers