The emperor Emmanuel/Immanuel/Manuel I Comnenus (? ~1123 - Constantinople, 1180), son of the Byzantine Emperor
John II, and emperor of the Byzantine Empire between 1143 and 1180.
It is the oldest reference that I found.
Another is Emmanuel/Immanuel/Manuel I of Trebisond (XIII c.)
the Warrior, son of
Alexis I of Trebisond.
At home, I will check the RAC (Repertori d'Antropònims Catalans).
Lumia
http://onomastica.mailcatala.com