also cream-puff, by 1859 as a kind of light confection, from cream (n.) + puff (n.). In figurative sense of "ineffectual person, weakling, sissy," it is recorded by 1935.
I remember my first campaign. My opponent called me a cream puff. That's what he said. Well, I rushed out and got the baker's union to endorse me. [Sen. Claiborne Pell, D-R.I., 1987]
As a salesman's word, "something that is a tremendous bargain," it is from 1940s.