(origin: Gaelic.) From Ceannsallach, authoritative, commanding, ruling. Walker, in his Historical Memoirs of the Irish Bards, relates the following story: Eochaidh, the then monarch, was defeated by Ena, King of Leinster, at the battle of Cruachan. In this engagement Ena killed Cetmathch, laureate bard to the monarch, although he fled for refuge under the shields of the Leinster troops. For this base deed the ruthless king was stigmatized with the epithet Kinsealach, that is, the foul and reproachful head, which name descended to his posterity.

Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.

KINSLEY. Probably a contraction of

Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.