After living together long enough, the Thunderbolts essentially develop their own secret language. Not on purpose, mind you. And they don’t even realize how strange it is until they have to work with other heroes and everyone stares at them like they have two heads.
It starts with the others making fun of Bucky for using outdated slang from the 1930s. He doesn’t care to break the habit or learn the modern slang, but he decides he has to get back at them somehow. So he starts making things up. At first, they’re close enough that only he can tell they’re fake, but then he starts pushing to see how weird he can get before they realize he’s fucking with them.
Once she figures it out, Yelena follows suit by mixing made up Russian phrases with her real ones. Alexei soon joins her (after she had to explain what she was doing multiple times so he wouldn’t ruin the joke), then Bob and John start throwing out fake Southern phrases left and right. And Ava gets to join in twofold, because she adds in fake and real phrase from both England and Argentina.
It doesn’t take them long to figure out they’re all doing the same bit, but it doesn’t take the fun out of it. They keep doing it, and some of the fake slang starts to stick. Eventually, they’ve created a mishmash of phrases pulled from across time and space, as well as from their own asses, that they all understand perfectly. It’s more secure than any code any intelligence agencies have ever come up with.
