What does YA -TA- HEY mean in native language?

The closest thing it sounds like that I know is pronounced "Yah-ah-Teh." It's Diné (Navajo) for "hello," or maybe "hello" is white-man for Yá'át'ééh.

I'm Lakota though so I may be wrong.

But there are well over 2000 Native American languages with countless dialects so it's just a shot in the dark.

Koskalaka "It actually means friend"

A dinner client just told me "It means the universe is good in you." Also informing me that some pronounce it "Yah-ha-Teh (or tey)" and some pronounce it "Yah-ah-Teh."