Flummadiddle has two meanings, and they go together better than you might expect. It is nonsense. It is also a pudding.

The nonsense sense comes first in the record we have. Green's Dictionary of Slang finds it in 1854, spelled flummerdiddle, in an American novel: What does she want of any more flummerdiddle notions? Through the rest of the century it means humbug and empty flattery — Green's has a farming writer in 1868 asking what's the use of so much flummy-diddle when plain common sense is enough. By 1903 it was being recorded on Cape Cod simply as foolishness.

The pudding is in M. Schele de Vere's Americanisms (1872), which describes the flummadiddle as a holiday-mess of New England fishermen, who lick their chops at the very mention of this oddly-named delicacy. The recipe is thrifty: stale bread, pork-fat, molasses, cinnamon, allspice, and cloves, made into a mush, baked in the oven and brought to the table hot and brown.

The link between the two is probably flummery. That word, too, meant both a soft sweet dish and empty talk. Green's suggests flummadiddle is flummery with diddle tacked on, and puts a question mark beside it; Wiktionary says apparently from, or related to, flummery. Either way, a mushy pudding and a mushy argument end up with the same name.

If you meet it labelled Victorian slang, be wary. The dates fit Victoria's reign, but the word is American, so it belongs to a different country's nineteenth century. For the British version of the same idea, see flapdoodle.