Updated: Sep 8
Fear a’ bhàta (or ‘The boatman’) is a Gàidhlig (Scottish Gaelic) song of heart break which is very popular in Scotland, "among English speakers too, having appeared in school books, standardised in print since the late nineteenth century".  It is said that it was written in the latter part of the 18th century by Sìne NicFhionnlaigh of Tong on the Isle of Lewis in the Outer Hebrides about Dòmhnall MacRath of Uig, about thirty-five miles away. Dòmhnall was a fisherman on Loch Roag , and the song is a lament concerning the author’s heartache and fears for his safety – or, alternatively, of his abandonment of her. The legend goes that the two married a year after the song was written.
The song first appeared in print in Cochruinneacha taoghta de shaothair nam bard gaëleach by Alexander Stewart and Donald Stewart (Dunedin: Clodh-bhuailt le T. Stiuart, 1804). The tune appeared in The Scottish Gael by James Logan in 1831, in which it was classified as an iorram (rowing song) and a slow air popular among Highlanders, and the full text was printed again in 1842 in Sar-Obair nam Bard Gaelach or The Beauties of Gaelic Poetry by John Mackenzie. It became well known among English speakers due to the romanticised depiction of the Highlands and Highlanders in late nineteenth century fuelled by Queen Victoria's attachment to the region. Newspapers reported that Fear a’ bhàta was sung in front of her on a visit in the early 1880s. 
The links between Rathlin Island (located 6 miles from the Antrim coast and 16 miles from the Mull of Kintyre) and Scotland go back to the 5th century, when the Dál Riata extended their kingdom from north Antrim to Kintyre and then to a portion of the western coast of Scotland, bringing the Irish language and customs, and crowning their first king, Fergus, who started the line of Scottish kings. Though the kingdom of the Dál Riata was extinguished within a few centuries, their descendants, the Scoti, united with the Picts to found the kingdom of Scotland. Rathlin was a part of these developments, and it was here that Robert the Bruce lived in exile before returning to Scotland to defeat the English in 1314. After the defeat of “Bonnie Prince Charlie” at the Battle of Culloden (1746) resulted in Highland clearances, many fled to Rathlin Island and the Hebrides.
Irish (Gaeilge), with heavy Scots Gaelic influences, was widely spoken on Rathlin Island, and was boosted by the Irish language revival in Antrim and Ireland at large in the late nineteenth and early twentieth centuries. Francis Joseph Biggar, Alice Milligan, Ada McNeill and Roger Casement were among those who advocated for the language in the north, and St Malachy’s Irish school was established on the island. Special study of the Rathlin dialect was made by Séamas Ó Searcaigh and Nils M. Holmer. Éinrí Ó Muirgheasa and Cosslett Ó Cuinn collected folk songs in the area, some of which were published in 1915 in a collection of Ulster songs. An Irish version of Fear a’ bhàta was collected from Kitty Glass, née Smith, a Rathlin resident born on the island in 1859. Her grandmother was Elizabeth Cameron of Campbeltown in Kintyre (see map above).  Another Irish version was collected by Sam Henry the vicinity of Coleraine, Northern Ireland and published some time between 1923 and 1939 in the Northern Constitution. This version had spread to the mainland from Rathlin. 
The wars and economic crises of the early decades of the twentieth century led to emigration from the island which resulted in a catastrophic collapse in the number of Irish speakers among the island's small population, and by the 1960s, the language was essentially dead. In 2002, a weekly class was established by Augustine (Gusty) McCurdy. 
This blog contains more on the language and folklore of Rathlin Island: http://rathlingaelic.blogspot.com
Text of Fear a bhata, A Rathlin Song from Ó Muirgheasa, Énrí, Céad de Cheoltaibh Uladh (B.Á.C.: M.H. Mac Giolla agus a Mhac, 1915) at Historic Irish Corpus 1600-1926, http://corpas.ria.ie/index.php?fsg_function=3&fsg_id=2451 I Théid mé suas ar an chnoc is áirde, Féach an bhfeic mé fear an bhata; An dtig thú anocht, nó an dtig thú amárach? Nó muna dtig thú idir is truagh atá mé. Luinneóg. A fhir an bhata, is na hó-ro eile, A fhir an bhata, is na hó-ro eile, A fhir an bhata, is na hó-ro eile, Céad míle fáilte gach áit an dtéid thú. II Tá mo chroidhe briste, brúidhte, Is tric na deoir a rith bho mo shúilean; An dtig thú indiu nó am bidh mé dúil leat, Nó an druid mé an doras le osna thuirseach? III Is tric mé fiosrach do lucht na mbatan An bhfeic iad thú, nó an bhfeil thú sábhailte; Acht is ann atá chuile h-aon dha ráidhte, Gur gorach mise má thug mé grádh dhuit. IV Gheall mo leannan domh gúna de'n tsíoda, Gheall é sin agus breacan riabhach, Fáinne óir, anns a bhfeicfinn íomhaigh - Acht is eagal liom go dean é dío-chuimhne. V Chan fheil baile beag anns am bidh thú, Nach dean thú gléas a chur do sgríos diot; Beir thú lámh ar do leabhar ríomhtha, Ag gabhail duanóg is ag buaidhreadh inghean óg. VI Ged adubhairt iad go rabh thu éadtrom, Cha do laghdaigh súd mo ghaol ort, Bha thú mo aisling anns an oidhche, Is anns' a' mhaidin ba mé dhá éinfheacht. VII Thug mé gaol dhuit is chan fhéad mé athrughadh; Cha gaol bliadhna, is cha gaol ráithche, Acht gaol ó thoiseacht, nuair bha mé 'mo pháiste, Is nach searg a choidhche mé 'gus claoidh' an bás mé. VIII Tá mo cháirdean go tric 'a ráidhte, Go bhféidí mé d'íomhaigh a chur ar dhío-chuimhne, Acht tá an chómhairle domh cómh diamhair Is a bheith a stad an tráigh 's an líonadh. IX Tá mo chroidhe-san a dul an áirde, Chan bho fhidleoir, chan bho chlársóir, Acht bho stiúrthóir an bhata, Is muna dtig thú abhaile gur truagh mar tá mé. X Bídh mé tuille go tuirseach deorach, Mar eala bhán is í in diaidh a réabtha, Guileóg báis aici, ar lochan féarach, Is cách uile in diaidh a tréigsin.
See https://terreceltiche.altervista.org/fear-a-bhata/ for original verses in Gàidhlig.
This TG4 documentary Ceol nan Oileán: Oileán Reachrainne (with English subtitles) tells the story of Rathlin Island and its music, language and links to Scotland. Fear a’ bhàta is mentioned from 7.20 - 10.20.
The version of Fear a’ bhàta below (Niamh Parsons) is the version which was sung on Rathlin Island.
The verison by Capercaillie is the original in Gàidhlig.
 Margaret Bennett, 'One and two percent: Scottish Gaelic folklore studies in Newfoundland and Quebec' in Lore and Language, Volume 15 (University of Sheffield, 1997), p. 130.
 John Stuart Blackie, Altavona. Fact and Fiction from My Life in the Highlands (1882), p.115
 Fear a’ bhàta, Terre Celtiche blog, https://terreceltiche.altervista.org/fear-a-bhata/
 Guest poster (21 and 22 January 2014) on https://mudcat.org/thread.cfm?threadid=121195