Tobirama as a teacher to Team Tobirama and having the children slangs getting infected into his vocabulary.
He just deal with their slangs so much that it just sounds regular to him but nonsense to anyone else. Even funnier if those slangs aren't even real, Team Tobirama just like coming up with weird shit. They are his students afterall, who's surprised?
Even funnier is if the adults start using the slangs too because they think Tobirama-sama is knowledgable, if I use it, I'll sound smart too.
Tobirama: "This topic isn't going anywhere. Leave it to the fishes."
(Team Tobirama intervention scene):
Danzo: "You guys keep arguing about the same thing. Just-just leave it to the fishes."
Hiruzen: "...leave it to the fishes?"
Danzo: "Well...um...the shimura clan used to live near the sea, so we say this to mean something is stupid...and erm...it's better to leave it to the fishes." (Totally not bullshitting. At all. Why would you even think that?)
Kagami: "Oh! That makes sense."
Tobirama: "That's a good idea. Let's put it in the forge."
(Team Tobirama intervention scene):
Kagami: "This is such a great day, sensei. I wish we could put it in the forge."
Tobirama: "Put it in the forge?"
Kagami: "It's an old Uchiha saying when something is good."
Tobirama: "I've never heard of it before."
Kagami: "Well, it's only allowed for smart people."
Tobirama: "Why the stipulation?"
Kagami: "Cuz only smart people know of it." *Hands on his hip, puffing out his chest. The perfect image of a proud man or in this case proud boy.*
(Also yes, Kagami is the little shit that can say absolute nonsense with a straight face.)
Tobirama: "Anija, it's perfectly fine. My experiment won't leave a Madara."
(Team Tobirama intervention scene):
Kagami: "You can't do that. You'll leave a Madara." (Kagami is totally, absolutely, most indubitably not upset at Madara currently.)
Hiruzen: "Leave a Madara?"
Kagami: "Well, Madara mean spot. So, it mean you shouldn't leave a spot or a stain on somebody."
