Psychiatry professor Sandor Rado (1890-1972) explained how the hyphenated term "obsessive-compulsive" arose.
Freud, like Kraepelin before him, called this entity [i.e., OCD] Zwangsneurose; by way of different translations, Zwang became "obsession" in London and "compulsion" in New York. Subsequent authors, apparently unaware of this fact and eager to ascertain what is meant by "obsessive" and what by "compulsive," settled for the unhappy designation "obsessive-compulsive."1
1Sandor Rado, "Obsessive Behavior" in S. Arieti and E. Brody, eds., American Handbook of Psychiatry, 2nd ed. (New York: Basic Books, Inc., 1974), vol. 3, p. 195. See also Berrios, 1996, p. 141.