He was educated by Reverend Philip Moore in the Douglas Grammar School and later at St John's College, Cambridge, where he took his LL.D degree in 1799.
The manuscript translation of the Old Testament from Deuteronomy to Job was nearly destroyed when the boat that Kelly was travelling on from Douglas to Whitehaven, struck rocks and became shipwrecked.
Kelly only managed to save the manuscript by holding it for five hours above the waves, before being rescued.
[6] This culminated in his A Practical Grammar of the Ancient Gaelic or Language of the Isle of Man, usually called Manks published in 1804.
Kelly's major life's work was A Triglot Dictionary of the Celtic Language, as spoken in Man, Scotland, and Ireland, together with the English.