AEthelweard was not an author of a Latin version of the collection of Old English annals where everything known of Cynric comes from.
thelweard (also Ethelward; d. c. 998), descended from the Anglo-Saxon King thelred I of Wessex, the elder brother of Alfred the Great, was an ealdorman and the author of a Latin version of the "Anglo-Saxon Chronicle" known as the "Chronicon thelweardi". 
The Anglo-Saxon Chronicle is a collection of annals in Old English chronicling the history of the Anglo-Saxons. 
 Everything known about him comes from the "Anglo-Saxon Chronicle". 
