The manuscript is kept at the National Library of Wales, Aberystwyth. It dates from around 1265, but is probably a copy of a lost 9th century original. The poetry would originally have been kept alive through oral tradition. The most well known poem contained within its pages is Y Gododdin, an early Welsh-language poem commemorating the warriors from Gododdin (Lothian in modern Scotland) who fell at the Battle of Catraeth (probably Catterick in North Yorkshire) around the year 600. Parts of this do appear to be contemporary with Aneirin. The other poetry, with no connection to this battle, includes, amongst others, a short poem for a child named Dinogad, describing how his father goes hunting and fishing.