As George Borrow explains in the preface to his translation of this work:
The Sleeping Bard was originally written in the Welsh language, and was published about the year 1720. The author of it, Elis Wyn, was a clergyman of the Cambro Anglican Church, and a native of Denbighshire, in which county he passed the greater part of his life, at a place called Y las Ynys. Besides the Sleeping Bard, he wrote and published a book in Welsh, consisting of advice to Christian Professors
source: The Sleeping Bard, p. iii
George Borrow claimed he had been asked to translate the book by a Welsh bookseller:
It was made by the writer of these lines in the year 1830, at the request of a little Welsh bookseller of his acquaintance, who resided in the rather unfashionable neighbourhood of Smithfield, and who entertained an opinion that a translation of the work of Elis Wyn, would enjoy a great sale both in England and Wales. On the eve of committing it to the press however, the Cambrian Briton felt his small heart give way within him: “Were I to print it,” said he, “I should be ruined; the terrible descriptions of vice and torment, would frighten the genteel part of the English public out of its wits, and I should to a certainty be prosecuted by Sir James Scarlett. I am much obliged to you, for the trouble you have given yourself on my account—but Myn Diawl! I had no idea till I had read him in English, that Elis Wyn had been such a terrible fellow.”
source: The Sleeping Bard, p. vi
George Borrow resumed work on the unpublished translation in 1854, shortly before his first Tour of Wales, and again in the latter part of 1857. The manuscript was then sent to George Borrow’s publisher, John Murray. In May 1858 George Borrow wrote to John Murray asking if he’d read the manuscript. John Murray declined the publish the book, writing:
There is no money in it
source: The Life of George Borrow, Clement Shorter, p. 207.
although he allowed George Borrow to use his name on the title page. In 1860 George Borrow privately printed 250 copies, in Yarmouth, using J. M. Denew as the printer, but with John Murray’s name on the title page. Printing was completed on 27 June 1860, at a cost to George Borrow of £15 16s. 8d.
George Borrow then published an anonymous review of this book in the article The Welsh and Their Literature, in John Murray’s Quarterly Review of January 1861. Knapp says this was a sales’ ploy, saying the review:
had the decisive result of selling off the whole edition in a month
source: The Life, Writings, and Correspondence of George Borrow, II. p. 196
At variance with the above statement is another given in Fraser and Collie:
In a letter dated 20 December 1909, William Webber, the Ipswich bookseller, told Frank Farrell: “I have seen somewhere a statement of his in his usual tall way with reference to this work that the entire impression was sold within the year whereas I found the whole of it at Oulton and sold it nearly intact to a particular London bookseller
source: George Borrow, A Bibliographical Study: p. 119
The Bulletin, Series 2, No. 1, p. 62 discusses this discrepancy, with neither statement appearing to be entirely true.