And "discord" means "disagreement", "lack of harmony", "arguments" in English. Even weirder name for a chat application in an even more commonly used language.

"Slack" associates pretty strongly with "slack off" (get no work done) too, so that one's also strange.

I think "Zulip" has the best naming of all these.

"Discord becomes strife cause that means kinda the same thing, strife becomes strafe cause that's a gamer term"

is the completely german-less train-of-thought I could imagine leading to this name