There was a real Jumbo (original name, Mumbo Jumbo) who passed away in 1885. Later, Jumbo became Dumbo, a slur created by Disney. Elephants aren't dumb. This Jumbo represented thread from the Clark's O.N.T. Thread Company. I don't believe Jumbo was paid for his endorsement. Kerr's thread company borrowed the Pachyderm as well.
