Joe Schmoe. A nobody. A delicious, savory nobody, maybe a little fried around the edges. Your ham-and-egger is someone who's done their best, but they don't have much to go on. They don't have a lot of experience, a little green, like
green eggs and ham. They're coming up through the ranks, making a name for themselves. They're in the fight, but they're not the winner.
There are a lot of rumors about the source of this term. It tends to go with boxing. Some people say that it comes from diner food, that boxers liked to rely on their ham and egg breakfasts while traveling around to different fights. Some say that in the coal mining days, this was a big slang word in coal areas: the loser in a fight got the ham and egg supper, or at least got paid just enough for fighting to afford that supper, while the winner left with the real cash prize. The ham-and-egger was the klutz, the perennial loser, just not cut out for the ring. They always got the ham and eggs.
Then there's the more positive spin on it. The populist movement sometimes had folks calling themselves "ham-and-eggers," like they were going to serve everyone up a big plate. Like they could get you a chicken in every pot. Maybe you'd keep the heat off and let that chicken lay you a pot full of eggs. Hey, they don't care what you do with the chicken. They're populists! They just want to provide you with a nice, preferably non-vegetarian meal.
So if you're being nice, it just means an average Joe. Not the perennial loser, just a somebody who's like all the other somebodies. Hey, you grab some random person off the street, chances are they'd trip over their feet in a boxing ring too. Next time you have some ham and eggs, think about it. We might slip into judging ourselves for messing up, in or out of the ring, but the fact is that everyone has something they're great at and something where they don't know enough not to mess up. That ham and egg supper can just remind us that we're all average Joes - and awesome Joes, and journeyman palookas, at once - inside.