Searchable collections of historical texts can lead to discoveries that transform our understanding of the provenance of certain words, phrases, and quotations. So it is with the term lunatic fringe.
In the Yale Book of Quotations, I gave the standard sourcing for this political/social expression:
[Of an international exhibition of modern art:] The lunatic fringe was fully in evidence, especially in the rooms devoted to the Cubists and Futurists, or Near-Impressionists.
—Theodore Roosevelt, Outlook, March 29, 1913
More recently, I searched for lunatic fringe in historical databases. To my surprise, I found many uses from before 1913—all in a very different sense from Roosevelt’s. Here are a few:
“The girls!” exclaimed Miss Lizzie, lifting her eyebrows till they met the “lunatic fringe” of hair which straggled uncurled down her forehead.
—Oliver Optic’s Magazine, February 1874
“LUNATIC Fringe” is the name given to the fashion of cropping the hair and letting the ends hang down over the forehead.
—Wheeling Daily Register, July 24, 1875
The “lunatic fringe” is still the mode in New York hair-dressing.
—Chicago Inter Ocean, May 24, 1876
It appears, then, that Teddy Roosevelt was playing on an existing phrase. His usage was a metaphorical extension of an expression previously applied to bangs—evidently, bangs that were considered outré. Fringe is still used in Britain for bangs, but the usage has been abandoned for so long in the United States that lexicographers were completely unaware of the coiffure-related prehistory of lunatic fringe.
And so a clever pun became a boring cliché of political discourse.