In Diné (Navajo) culture it is an expression used to acknowledge something in
disappointment and/or apathy, or
even in a comedic condescending
way.
It can be prolonged to “wahhh” depending on context and how the user decides to use.
Rez
dude - “
Hey did you hear your uncle so-and-so picked up a new ride?”
Rez chick - “No huh uh, what did he get?”
Rez
dude - “don’t even know, it’s an old used truck.”
Rez chick - “Wahhh”