"sideshow freak," 1916, U.S. carnival and circus slang, perhaps a variant of geck "a fool, dupe, simpleton" (1515), apparently from Low Ger. geck, from an imitative verb found in North Sea Gmc. and Scand. meaning "to croak, cackle," and also "to mock, cheat." The modern form and the popular use with ref. to circus sideshow "wild men" is from 1946, in William Lindsay Gresham's novel "Nightmare Alley" (made into a film in 1947 starring Tyrone Power).
"great hunter," 1712, in ref. to the biblical son of Cush, referred to (Gen. x.8-9) as "a mighty hunter before the Lord." It came to mean "geek, klutz" by 1983 in teenager slang, for unknown reasons. (Amateur theories include its occasional use in "Bugs Bunny" cartoon episodes featuring rabbit-hunting Elmer Fudd as a foil; its possible ironic use, among hunters, for a clumsy member of their fraternity; or a stereotype of deer hunters by the non-hunting population in the U.S.)