I don't have a TON to add, other than I love the term Slap Dick so goddamn much. It's such baseball hillbilly slang
The first time I heard it was from my hillbilly college pitching coach. He was such a wild asshole I wouldn't even know where to begin the stories. The first time I heard Slap Dick was when he was using slow motion video software to explain, in detail, just how much I sucked:
What kinda slap dick change up you call that? I aint teaching that fucking bullshit.
Slap Dick Change Up.
This is a guy who once made one of our (future 11th round) pitchers leave an offseason conditioning session to go get a Big Mac from McDonalds and then come back and eat it in front of us while we ran wind sprints because he thought the pitcher was getting too fat. He said "I want you to eat fast food while everyone else works because I know you don't want it as bad as those motherfuckers." So my buddy got in his car, went to McDonalds and came back with his burger. He sat there and ate it. He said it was the tastiest burger he's ever had in his life. We were all so jealous.
That guy was a real son of a bitch. Not a slap dick though. Slap dick is when you're just kind of a fuck. It's like being a beta but worse. You're a jagoff too. And brain dead and a bunch of other mean stuff.