dingbat (n.)

1838, American English, apparently originally the name of some kind of alcoholic drink, of unknown origin. It has joined that class of words (such as dingus, doohickey, gadget, gizmo, thingumabob) which are conjured up to supply names for items whose proper names are unknown or not recollected. Used at various periods for "money," "a professional tramp," "a muffin," "male genitalia," "a Chinese," "an Italian," "a woman who is neither your sister nor your mother," and "a foolish person in authority." Popularized in sense of "foolish person" by U.S. TV show "All in the Family" (1971-79), though this usage dates from 1905. In typography, by 1912 as a printer's term for ornament used in headline or with illustrations.

About 10:30 o'clock there was a snap of breaking metal, and the machine was stopped. It was discovered that the gilderfluke had come into contact with the dudad which operates the dingus on the diaphason, thereby letting the Johnson bar oscillate as it were between Alpha and Omega, thus preventing the dingbat from percolating the perihelion of the gazabo, and causing the dofunny on the parallelogram to drop into oblivion. [from an Illinois newspaper's account of a production delay caused by a Linotype machine breakdown, reprinted in Inland Printer, Chicago, February 1903]