1997: There was a powerful hersir in Sognefjord called Bjorn, who lived at Aurland; his son Brynjolf inherited everything from him. — ‘Egil's Saga’, tr. Bernard Scudder, The Sagas of Icelanders (Penguin 2001, p. 52)
Meaning of hersir for the defined word.
Grammatically, this word "hersir" is a noun, more specifically, a countable noun.