One of the signs that
the US Ku Klux Klan
uses. Like other secret societies, the Ku Klux Klan uses its own
symbols, although they (like the garb with the hoods) have their roots
in Spanish Catholic symbolism. The Klan was created after the American Civil
War by some of the defeated white southerners with the intention of
keeping the recently freed slaves in some control.
The Klan ultimately developed into a fascist, reactionary, petit bourgeois organization, their spear aimed at all that was new, humanistic, and liberal.
Compare with , a sign on maps and nautical charts for lighthouse.
See also for information concerning a similar organization in Europe 500 years earlier.