April 24th 1567 saw the first printed book in Gaelic published in Edinburgh.
"Foirm na n-Urrnuidheadh," a Gaelic translation of the Book of Common Order, was the first book printed in Scottish Gaelic. This work, also known as "Knox's Liturgy," was a significant undertaking, especially considering the language's complexity and the time it took for the New Testament to be published in Gaelic. Only three copies of this first Gaelic print are known to exist, including the only one in Scotland.
After the Reformation there was a strong impetus, sponsored primarily by the Campbell Earls of Argyll, to evangelise the Highlands and Islands, where Gaelic rather than Scots was spoken. John Carswell, Bishop of the Isles, adapted John Knox’s Book of Common Order into Scottish Gaelic. It was a hugely ambitious undertaking, particularly considering it would be another two centuries before the New Testament was finally published in vernacular Gaelic.
You can view the whole book at the link below.
