It was the symbol for the "ban the bomb" movement in the early sixties in Britain. It was brought from there and used to represent the "peace movement" in the US. The only peace which resulted from this movement was the peace of the grave suffered by the victims of totalitarian regimes. The irony is the participants in the movement feel they were on the the side of right and so feel not one iota of shame despite the lessons of history.
I was shown a pamphlet one time that the peace symbol (chicken foot) was really the broken Cross of Jesus Christ. I don't know if this is true or not...just my 2 cents worth. I have never liked the peace symbol.