Eumon Kerman does not appear in-game, but is one of the few non-random Kerbals named in any game text.
Eumon is one of the top minds in the rocket engineering industry. He was selected by researchers (presumably with Rockomax Conglomerate) to plan and build a revolutionary new engine type because he was crazy enough to do it. However, he failed miserably at the job and the world ended up with the Rockomax Mark 55 Radial Mount Liquid Engine.
Nothing else is stated in-game about Eumon Kerman. It may be reasonable to assume he's merely a name for a funny anecdote from Kerbal rocket manufacturing.