Years ago. A myth arose from humans. The origin of the myth or what brought it up remains a mystery.
The reason it was known as a myth is because not a single person was ever able to provide proof of it. Adventurers travelled the lands in search of it but found nothing.
Some of them were also never found after going in search for it. They disappeared without leaving a trace in the world. Sailors and pirates scoured the seas. But failure was all they found in the myth.
Ships sunk to the bottom of the ocean in thousands and possibly millions. Some gave up and some persevered, but the triangle of the lost was never located.
The Triangle, or rather.... myth, was of a place unknown to anyone. A place in which things that were lost to the world were found. Well, not really found. Rather, where they were.
The triangle of the lost. That's the name they came to call it. The people who at least knew or believed in the myth that is.