Why the title Duck Soup?!?!?!
Earlier (in 1927), director Leo McCarey had made a two-reel Laurel and Hardy film with the same title - and he used it again. The film's title uses a slang phrase familiar in early 20th century America. It means anything "simple" or "easy", or alternately, a "gullible sucker" or "pushover."
The film has become a classic--the ultimate send-up of power-hungry dictators. Groucho supposedly provided the following recipe to explain the title: "Take two turkeys, one goose, four cabbages, but no duck, and mix them together. After one taste, you'll duck soup for the rest of your life."
(Under the opening credits, four quacking ducks [stylized four Marx Brothers] swim & simmer in a heating kettle.)