Sri Lanka

Let me make one thing clear from the outset: I don't have a problem with Serendip being the Persian name for Sri Lanka (Wikipedia: 'The Persians and Arabs referred to it as Sarandib (the origin of the word "serendipity") from the word Cerentivu'); and to be fair, this was the actual question, the rest being just background information. So no real problem with the question.

Having said that, I don't know where the question setter got the idea that Sri Lanka means Resplendent Island. Well, I do have an inkling – see below - but I don't believe it's true.

Wikipedia is no help in this matter; it gives lots of former names for the island, but it doesn't give an English translation for the current name.

The best explanation I could find was in this queries forum, which appears to be written by a knowledgeable local. It says: '"Sri" in Sinhala is a honoring prefix, in the line of "His/Her Excellency" and "Honorable". "Lanka" is a name used for Sri Lanka since ancient times, among others.'

So 'Sri' means 'Honorable' rather than 'Resplendent', and 'Lanka' doesn't mean 'island' but is the ancient name of this particular island.

Top result in a Google search for "sri lanka resplendent" (apart from a few commercial pages) was this article in The Independent. This does refer to Sri Lanka as '[the] Resplendent Isle' – in several places, including its title – but nowhere does it say that this is a translation of its Sinhalese name. Seems it's just a nickname – a bit like referring to Ireland as the Emerald Isle.