"a small, light, round, spongy cake made with eggs," usually eaten buttered and toasted, 1703, moofin, possibly from Low German muffen, plural of muffe "small cake;" or somehow connected with Old French moflet "soft, tender" (said of bread). The historical distinction of the muffin from the crumpet is not entirely clear and the subject is involved. In American English the word was extended to a sort of cup-shaped bun or cake (often with blueberries, chocolate chips, etc.); hence muffin top "waistline bulge over tight, low jeans" (by 2005), from resemblance to baked muffins from a tin. Muffin-man "street seller of muffins" is attested by 1754.
Why sit we mute, while early Traders throng
To hail the Morning with the Voice of Song?
Why sit we sad, when Lamps so fast decline,
And, but for Fog and Smoke, the Sun would shine?
Hark! the shrill Muffin-Man his Carol plies,
And Milk's melodious Treble rends the Skies,
Spar'd from the Synagogue, the Cloathsman's Throat,
At measur'd Pause, attempers every Note,
And Chairs-to-mend! with all is heard to join
Its long majestic Trill, and Harmony divine.
["The Black Bird and the Bull-Finch," 1777]
1821, in a German context, "a hangover," American English colloquial, from German Katzenjammer "hangover" (18c.), also figuratively, in colloquial use, "remorse of conscience, vow to mend one's ways," literally "wailing of cats, misery of cats," from katzen, combining form of katze "cat" (see cat (n.)) + jammer "distress, wailing" (see yammer (v.)).
Pleasure can intoxicate, passion can inebriate, success can make you quite as drunk as champagne. The waking from these several stages of delights will bring the same result--Katzenjammer. In English you would call it reaction; but whole pages of English cannot express the sick, empty, weary, vacant feeling which is so concisely contained within these four German syllables. ["Blackwood's Edinburgh Magazine," August 1884]
Katzenjammer Kids "spectacularly naughty children" is from the title of the popular newspaper comic strip (based on the German Max und Moritz stories) first drawn by German-born U.S. comic strip artist Rudolph Dirks (1877-1968) in 1897 for the "New York Journal." Hence, katzenjammer in the sense "any unpleasant reaction" (1897). The strip was temporarily de-Germanized during World War I:
"THE SHENANIGAN KIDS" is the new American name for the original "Katzenjammer Kids." Although the original name and idea were pure Holland Dutch, some people may have had the mistaken impression that they were of Germanic origin, and hence the change. It is the same splendid comic as in the past. [International Feature Service advertisement in "Editor & Publisher," July 6, 1918]