The language changed significantly due to the influence of Norse after the Viking invasion of the Isle of Man and its relative political isolation from the rest of the Gaelic speaking world in later centuries.

[4] Despite this, Cregeen noted the negative attitudes towards it and the low-prestige nature of the language on the Isle of Man in the preface to his dictionary: I am well aware that the utility or the following work will be variously appreciated by my brother Manksmen.

Those who reckon the extirpation of the Manks a necessary step towards that general extension of the English, which they deem essential to the interest of the Isle of Man, will condemn every effort which seems likely to retard its extinction.Cregeen began work on the dictionary in 1814.

He did not work completely alone, but was aided by several Manx clergymen, notably Reverend John Edward Harrison, a vicar of the parish of Jurby, who supplied him with additional information.

Compiling the dictionary took Cregeen over 20 years of meticulous research, travelling throughout the island, visiting farms and cottages and collecting words, phrases, and proverbs from the people he met.

Reverend John Kelly had attempted to do so in his A Triglot Dictionary of the Celtic Language, as spoken in Man, Scotland, and Ireland together with the English, but much of this was destroyed in a fire during publishing.

[3] In more recent years, with the continued revival of the language in the Isle of Man, Culture Vannin has celebrated Cregeen's work by selecting some of the lesser known words from his dictionary and posting them on social media.