What is "ottir"

Earl Ottir (; , 'Count Oter'; died 918), also known as Ottir the Black , was a jarl who occupied a prominent position among the Norse of Britain and Ireland in the early 10th century. He is believed to be the founder of the settlement, Loch dá Caech (present day Waterford) in the year 914. From 917 to his death in 918 Ottir was a close associate of the powerful overking Ragnall ua Ímair, although they are not known to have been related.