A connected Old Irish form of the name appears from the 6th to the 10th centuries in the Annals of Ulster and later sources, which contain repeated references to "rex Fortrenn", ("the King of Fortriu"), "la firu Fortrenn" ("the men of Fortriu") and "Maigh Fortrenn" ("the plain of Fortriu"), alongside references to battles occurring "i Fortrinn" ("in Fortriu"). These are examples of a common pattern of Goidelic languages rendering with an "f" what in Brittonic languages is "U"/"V", "W" or "Gw". The word "Fortriu" is a modern reconstruction of a hypothetical nominative form for this word that has survived only in these genitive and dative cases. Anglo-Saxon sources, from the "Anglo-Saxon Chronicle" in the 6th century to Bede in the 8th century, refer to the group using the Old English form of the name "Wærteras".