According to Disney A - Z
Goofy's original name was "Dippy Dawg" then became "Dippy the Goof" and finally "Goofy." "...Goofy was part of the gang that included Mickey, Minnie, Pluto, Clarabelle Cow, and Horace Horsecollar. In the newspaper comic strips, this new character was first given the name Dippy Dawg. A 1938 book indicated the first change to Dippy's name, The Story of Dippy the Goof and by 1939 the final change was made with the release of the cartoon Goofy and Wilbur. Goofy was created as a human character, as opposed to Pluto, so he walked upright and had a speaking voice..."
Goofy's original name was "Dippy Dawg" then became "Dippy the Goof" and finally "Goofy." "...Goofy was part of the gang that included Mickey, Minnie, Pluto, Clarabelle Cow, and Horace Horsecollar. In the newspaper comic strips, this new character was first given the name Dippy Dawg. A 1938 book indicated the first change to Dippy's name, The Story of Dippy the Goof and by 1939 the final change was made with the release of the cartoon Goofy and Wilbur. Goofy was created as a human character, as opposed to Pluto, so he walked upright and had a speaking voice..."