What is "tirechan"

Tírechán was a 7th-century Irish bishop and biographer of Saint Patrick. Tírechán wrote his untitled memoir (so-called because it is written in the first person, as though the author was Patrick) sometime after the death of his mentor, Ultan of Ardbraccan, in 657. The work survives in the manuscript The Book of Armagh.

Tírechán's account, which J. B. Bury dated to the 660s or 670s, is frequently compared with the more-or-less contemporary narrative of the monk Muirchu moccu Machtheni.