"Thunder and lightning are barnburners sometimes"

Herbert D.A. Donovan dates the use of the term "Barnburners" to 1842, although "[t]he use of the term is not common before 1843." The most likely origin

is, that the name grew out of a slighting remark that the policy of the Radicals in connection with public works resembled that of the legendary Dutch farmer who had burned down his barn to rid it of the rats -- the implication being that the Barnburners were willing to destroy the public works and corporations to stop the abuses connected with them. This explanation was given by speakers on both sides during discussion in the legislature . . ..

The term of ridicule was, predictably enough, eventually adopted by the targets as a badge of honor:

[I]n 1847, at the celebrated Herkimer convention, Samuel Young, one of their oldest and ablest leaders, accepted the designation. "Gentlemen," said he, "They call us barnburners. Thunder and lightning are barnburners sometimes; but they greatly purify the whole atmosphere, and that, gentlemen, is what we propose to do.."

About the illustration:

A humorous commentary on Barnburner Democrat Martin Van Buren's opposition to regular Democratic party nominee Lewis Cass. Van Buren and his son John were active in the Free Soil effort to prevent the extension of slavery into new American territories. In this he opposed the conservative Cass, who advocated deferring to popular sovereignty on the question. In "Smoking Him Out," Van Buren and his son (wearing smock, far right) feed an already raging fire in a dilapidated barn. (radical New York Democrats supporting Van Buren were referred to as "Barnburners" because in their zeal for social reforms and anticurrency fiscal policy they were likened to farmers burning their barns to drive out the rats). On the left, Lewis Cass prepares to leap from the roof of the flaming structure while several rats likewise escape below him. The artist seems to favor Van Buren, and his attempt to force the slavery issue in the campaign. The Free Soilers, unlike the Democrats, supported enforcement of the Wilmot Proviso, an act introduced by David Wilmot which prohibited slavery in territories acquired in the Mexican War. John Van Buren, adding another pitchfork of hay to the flames, exclaims, "That's you Dad! more 'Free Soil.' We'll rat'em out yet. Long life to Davy Wilmot."