Blathewyc or Blathewic (from Irish Uí Blathmaic, meaning 'descendants of Blathmac'[1]) is the name of several historical territorial divisions in what is now County Down, Northern Ireland.
It is the anglicised name of an ancient Irish túath, ruled by the Uí Blathmaic, later becoming a barony, bailiwick, and county in the Anglo-Norman Earldom of Ulster.
[1] Blathewyc is an anglicisation of the Irish tribal name Uí Blathmaic, which means the "descendants of Blathmac".
Blathmac is cited as being the son of Áed Róin mac Bécce Bairrche, an over-king of Ulaid who died in 735.
"[2] After the invasion of Ulaid in 1177 by the Norman knight John de Courcy, and its subsequent conquest, the neighbouring districts of Aird Uladh and Uí Blathmaic were combined to form a county, which was styled as "Comitatus de Arde" and "Comitatus Novae Villae".