AS is used to refer to the Germanic peoples, i.e. Angles and Saxons and others, who settled in what today we call England in the 400 years after the 5c when the Romans left and before the *Viking incursions of the 9c and later. When speaking of the language, 'Old English' is preferred to 'Anglo-Saxon'. [< OldEngl. Angulseaxe ]
Cf. Angles
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.