As far as I know the term 'English' as applied to the English language is first evidenced in King Alfred's translation of Bede's Ecclesiastical history. As to how much earlier than that is was being used in any context or how it was pronounced at any time or in any location - has anyone got a time-machine handy? Seriously though, I don't think that we know although there have been various attempts to provide some kind of retrospective standard. I prefer Campbell's (Old English Grammar) approach - for example - para. 48 ' Old English scribes are very consistent in their representation of accented vowel sounds, but every accented syllable did not have the same vowel sound in every dialect, or even at every time within one dialect. Hence there is a great diversity of spelling in Old English, arising not from inconsistency in the values of the symbols, but from diversity of sound.'
