I put that on chawls!
You call out the name of the X men's leader to make sure everyone knows you're telling the truth. It's like swearing on a dead grandma's last breath.
I put that on chawls! I swear on Professor X's soul!
Chawls! I'm not lying, I'm telling the truth!
If I don't tell the truth, I'll be the next X man to die! Chawls!