What was the original meaning of the peace symbol in the picture?

After the bombing of Hiroshima and Nagasaki by the U.S. during WW2, other countries developed their own atomic bombs. In Britain, a group people who were concerned about the large number of nuclear weapons all over the world united to form a group that advocated for peace and getting rid of large destructive weapons of war. These people advocated for something called nuclear disarmament, and so they called themselves the Campaign for Nuclear Disarmament.

The CND was founded in 1958, and that same year they asked the artist Gerald Holtom to design a symbol for them - one that would symbolize the end of war and destruction and serve as a sign of peace and unity. That symbol is now universally known as the peace symbol. The symbol is a superposition of the semaphore signals (a type of messaging using flags) for the letters "N" and "D", taken to stand for nuclear disarmament.