Ellan Vannin (the Manx-language name of the Isle of Man) is a poem and song, often referred to as "the alternative Manx national anthem", the words of which were written by Eliza Craven Green in 1854 and later set to music by someone called either J. Townsend or F. H. Townend (sources vary).
The Manx-language name Ellan Vannin is commonly mispronounced in renditions of the song, including in the Bee Gees version, since written Manx uses an orthography based on Welsh rather than Irish/Scots gaelic, which does not accurately transcribe the "ʲə" sound found in the word for "island" in spoken Manx Gaelic. The correct pronunciation is [ˈɛlʲən ˈvanɪn].
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The Bee Gees recorded a version for Isle of Man charities. They also included the song in their world-tour as a show of pride in the place of their birth.