given name of Michigan J. Frog is derived from  the one song he sings in this cartoon that writer  Michael Maltese (qv) wrote especially for him, "The Michigan Rag".  The last name is derived from his species, in the same fashion as  Bugs Bunny, Daffy Duck et al., and the middle initial is derived  from the fact that all cartoon characters are considered to have "J"  as their middle initial (such as in _"Simpsons, The" (1989)_ (qv)),  unless evidence exists to the contrary.