In 1964, Leon Bibb (I'm pretty sure) is quoted by Newsweek and Sing Out! magazines as saying, "I suppose in America I'm a protest singer just by my presence on stage. But not when I'm abroad. But I don't want to one of those Negroes who abstract their art from the struggle. I want to be counted in."

Also in 1964 in The Realist, an underground humor magazine, Paul Krassner wrote "After leaving school I knew I had to do something that would pay a lot of money and not require much work, so I became a protest singer."

In 1965, Life and Billboard magazines both used the term, and it takes off.

~ Becky in Tucson