Sri Lanka's many name changes over the centuries are a reflection of its fascinating history The island currently going by the name of Sri Lanka has had a string of other identities and has been known under a range of nicknames and pseudonyms. To Prince Vijaya and the founding fathers it was, in their Sanskritie language, Tambapanni, after the copper-coloured beach on which they landed, either at Mannar or Puttalam but in any case on the west coast. In the reign of the Roman Emperor Claudius, a sea captain working for Annius Plocamus, a tax collector in the Red Sea, suffered the misfortune of catching a monsoon that swept his boat off course and dumped him on the island 15 days later. For him, and other Roman and Greek callers, Tambapanni was too much of a mouthful and became Taprobane. The geographer Ptolemy rang a slight change by showing it as Taprobanam on his famous 2nd-century AD map. 
Arab traders could have told Annius Plocamus's captain that if he waited a while a different monsoon would blow him back to Arabia or, if he liked, East Africa. They relied on these winds to go back and forth, knew the island well and called it Serendib. This name is a corruption of the Sanskrit Sinhaladvipa. Cosmas Indicopleustes, the Byzantine author of Christian Topography, twisted the Arabic into Sielediba, but the 18th-century English novelist Horace Walpole stuck to the original for his fairy tale, The Three Princes of Serendib, and used it to coin "serendipity," meaning discovery by happy accident. Another variant, Sirinduil, as yet awaits a neologist to give us a definition of "sirinuility."  Edward Barbosa, a Portuguese captain who visited in 1515, tried to persuade his countrymen to adopt Tennaserim, which in some ancient Indian language meant "Land of Delights," but they had already settled on Celao, which had started as the Chinese Si-lan and, thanks to medieval Europeans like Marco Polo, became Seylan. The Dutch worked out their own derivation to produce Zeilan; the English compromise was Ceylon. 

Through all of this, the Sinhalese had long ago decided it was lanka, and it officially changed to Sri Lanka in 1972 (the prefix means "holy" or "beautiful"). The words Prajathanthrika Samajavadi Janarajayi (Democratic Socialist Republic) were tacked on in 1978. The trick with these tongue twisters is to try and pronounce everything, but the complications of long and short vowels, and aspirated and retroflex consonants, will help you trip up. Your mispronunciations will no doubt be forgiven; Sri Lankans are used to people getting their name wrong.