“Thong” can mean a type of sandal, also known as flip-flops, but it’s also the name of a type of underwear or swimsuit bottom that’s basically a string in the back.

I grew up calling flip flops “thongs”, but as I got older, people were almost exclusively using that term for the underwear, so I switched terms to avoid confusion.

https://en.wikipedia.org/wiki/Flip-flops https://en.wikipedia.org/wiki/Thong