Unable To Rest Their Local Phrasing

I work in a cafeteria in a popular tourist place. We get customers from all over the world, many of whom speak English. While English is my third language, I would say I’m fairly fluent in it.

A middle-aged lady, most likely from the US by her accent, comes to the counter. She seems a bit upper-class in her dressing and actions, but as I’m from a small village in the middle of nowhere, I would have said that about pretty basically anyone from a bigger city!

Customer: “Could you tell me where your restroom is, please?”

I am very confused as I have never heard that word before.

Me: “Um… I’m sorry?”

Customer: *Scoffs.* “Restroom. Where is your restroom?”

Me: “Restroom?”

The customer now has a bit of an annoyed tone, like “I cannot believe you’re making me say it.”

Customer: “Toilet! Where is your toilet?!“

Me: “Oh! Just around the corner over there.”

The customer huffed and went on her way. I cannot remember if she thanked me because I was so confused as to why you would call a toilet a “restroom”. Who would go there to rest or relax?

Later on, I did find out that there are quite a few different words in English for toilet, and that “restroom” is another word for a public toilet. But I’m still confused as to why it was such a hassle to just call it a toilet.