headcannon: when dallas first met johnny, johnny had mumbled his name really quietly. so, instead of hearing “johnny cade” dallas heard “johnny cake”. so, he started calling johnny that, it stuck, and soon the rest of the gang would call johnny that too.
“You take up for your buddies, no matter what they do. When you’re a gang, you stick up for the members. If you don’t stick up for them, stick together, make like brothers, it isn’t a gang anymore. It’s a pack. A snarling, distrustful, bickering pack like the Socs in their social clubs or the street gangs in New York or the wolves in the timber.”