This was the original name of the current country of Sri Lanka. It was named Ceylon until 1972.
I couldn’t find any specific reference to where “Ceylon” came from. The Portuguese used it when they occupied the island in the early 1600s, and it carried forward. It was finally rejected as a “slave name” or “colonial name.””
From a related question on Quora that was answered by several Sri Lankans:
The word Ceylon has no meaning in any of the official languages of Sri Lanka. It is just a name coined by the colonial rulers that was elected to be replaced when the country gained its freedom. […] It is a name that implies a long history of suppression which we’d not rather remember every time our country is mentioned.
Why I Looked It Up
It came up in a book about the oil industry.