Same as it means in Spanish.
Let your inner 12 year old have a little giggle.

Indulge me.

Lol. I’ll indulge you, although I’m pretty sure you know already. It means teats or breasts.

But, supposedly there is a Native American tribe with the name Teton in the area (I think they were Sioux) so there are multiple theories on how the mountains actually got their name.

I only know the story because my parents vacationed in the area many years ago. I remember my mom telling me they sell t-shirts with two mountains (one on each breast) and it says Grand Tetons.

Bounteous Boobage.
Tremendous Tits.
Classic Cleavage.
Magnificent Mammaries.

Because those French beaver trappers dreamed big ;)

Thank you.
My father knew much of the history of the Wyoming country. It was he who told our family of the first French trappers in the area who named the Tetons “The Great Breasts.” Although probably not translated in quite the same exact words.
There are those who doubt me and I wanted to see if someone else would confirm what I had been told.