In college I took a “Biology of the Sierra Nevada” class with a very interesting professor. His mother was Mi-Wok and had lived with her family in Sequoia National Park a little way south of Yosemite.
On the first day of class we walked in and sat down at our desks. The professor moved to the front of the room. He quietly looked at the class then in a rough voice he said, “I’m going to teach you all how to not sound like IDIOTS!”
He looked at one young man, “What mountains are we studying?”
“The Sierra’s” the student replied.
“Wrong. You’re an idiot.”
He looked at another young man, “What mountains are we studying?”
“The Sierra’s?” he replied meekly.
“Wrong. You’re an idiot too. Is everyone in here an idiot?” No one moved a muscle. “We are studying the Sierra Nevada, people. Nothing gets my goat more than to hear someone say ‘Sierras’. It’s already plural! Sierra is ‘mountains’ in Spanish. It’s not ‘mountains’s’. If you get nothing else out of this class you’ll know at-least that. It’s ‘the Sierra Nevada’ or simply ‘The Sierra’. Know that and you won’t sound like an idiot anymore.”
I guess I learned my lesson well because to this day I say ‘Sierra’ not ‘Sierras’. And now, you will too.