King was a member of an Irish bardic family, who were residents of the barony of Kilcoursey, County Offaly, known as Fox's Country.
Writing in 2001, McCaughy states "What we can say is that the Muircheartach Ó Cionga that we are concerned with in this study was one of a learned poetic family of the name who are referred to quite frequently in the sources, some of whose poetry survives (a good deal of it religious), and that they are located in the barony of Kilcoursey in Fox’s Country."
[2] King was employed from 1627 by William Bedell (later Bishop of Kilmore) to teach Irish to himself and students at Trinity College, Dublin.
This provided him with an income while he translated the Old Testament and Apocrypha into Irish, having been selected as an acknowledged master of the language, in both prose and verse.
He was accused of secretly attending Catholic mass with his family, inappropriately administering baptism and holy communion.
When his son asked him for money, he said, "Poor slave; woe’s me, that am going to hell to get you maintenance", insinuating that he was conformable against his conscience.
"Bedell defended him, concerned that attacks on King's character would detract from the reputation of the translation, and said as much in a letter to Thomas Wentworth, 1st Earl of Strafford, dated December 1638.