Green’s Dictionary of Slang

(US campus) one of various types of muffin or biscuit.

1878		Placerville Mountain Democrat (CA) 31 Aug. n. p.: At the Methodist school at Wilbraham, Mass, the name ‘dingbat’ has already been applied to a large raised biscuit that is brought to the table and eaten with butter or molasses in the morning. It’s palatable to the hungry, but is about as indigestible as a brickbat.
1895		DN I. 387: Dingbat. Mr. Philip Hale, of the Boston Journal, has been collecting information . . . concerning this word. The following definitions appear: — [...] (6) In some of the N.E. schools, the word is student slang for various kinds of muffins or biscuit.
1900		E.H. Babbitt ‘College Words and Phrases’ in DN II:i 32: dingbat, n. Muffin or bun.