Laudator Temporis Acti

Aristophanes, Knights 41 (Demos described by one of his slaves; tr. Jeffrey Henderson):

...with a farmer's temperament, a bean chewer, prickly in the extreme...

...ἄγροικος ὀργήν, κυαμοτρώξ, ἀκράχολος...

Alan H. Sommerstein ad loc.:

a bean-chewer: it is not quite certain what this epithet implies, but most probably it denotes a peasant: Greeks chewed beans to stay awake and concentrate when doing monotonous work (Lys. 537 with schol.) and bean-chewing may well have had associations with rusticity, low social status, and/or low intellect, much as gum-chewing or tobacco-chewing may today. Compare the line of an unknown comedy cited by the Suda (κ 2578, "No bean-chewing Attic will judge between these men", i.e. the judge will, on the contrary, be one who has the intelligence to come to the right decision. These is no reason to believe that the epithet has anything to do with the one-time use of beans as lottery-tokens in Athenian elections.

Liddell-Scott-Jones favor the explanation related to elections.