"This forked symbol was adopted as its badge by the Campaign for Nuclear Disarmament in Britain, and originally, its use was confined to supporters of that organization. It was later generalised to become an icon of the 1960s anti-war movement, and was also adopted by the counterculture of the time. It was designed and completed February 21, 1958 by Gerald Holtom, a commercial designer and artist in Britain. He had been commissioned by the CND to design a symbol for use at an Easter march to Canterbury Cathedral in protest against the Atomic Weapons Research Establishment at Aldermaston in England."
"The symbol itself is a combination of the semaphoric signals for the letters "N" and "D," standing for Nuclear Disarmament. In semaphore the letter "N" is formed by a person holding two flags in an upside-down "V," and the letter "D" is formed by holding one flag pointed straight up and the other pointed straight down. These two signals imposed over each other form the shape of the peace symbol. In the original design the lines widened at the edge of the circle."
From Wikepedia, FWIW. I had thought it was a stylized ICBM launching but what do I know? (Well, at least more than Sheehan, but that's still not saying much!)
Interesting...thanks for doing the research :)