It’s from drinking all that burnt coffee.

Starbucks, Forbes/Shady, Squirrel Hill.
A barrista makes a loud, evil laugh:

Barrista #1: Wow, that was some cackle.
Barrista #2: I thought you knew: Under this apron… PURE EEEEVIL!
Barrista #3: I don’t even think that kind of cackle is in my repertoire.

— Overheard by Connor