The history of our dialects in the earliest periods of which we have any record is necessarily somewhat obscure, owing to the scarcity of the documents that have come down to us.  The earliest of these have been carefully collected and printed in one volume by Dr Sweet, entitled The Oldest English Texts, edited for the Early English Text Society in 1885.  Here we already find the existence of no less than four dialects, which have been called by the names of Northumbrian, Mercian, Wessex (or Anglo-Saxon), and Kentish.  These correspond, respectively, though not quite exactly, to what we may roughly call Northern, Midland, Southern, and Kentish.  Whether the limits of these dialects were always the same from the earliest times, we cannot tell; probably not, when the unsettled state of the country is considered, in the days when repeated invasions of the Danes and Norsemen necessitated constant efforts to repel them.  It is therefore sufficient to define the areas covered by these dialects in quite a rough way.  We may regard the Northumbrian or Northern as the dialect or group of dialects spoken to the north of the river Humber, as the name implies; the Wessex or Southern, as the dialect or group of dialects spoken to the south of the river Thames; the Kentish as being peculiar to Kent; and the Mercian as in use in the Midland districts, chiefly to the south of the Humber and to the north of the Thames.  The modern limits are somewhat different, but the above division of the three chief dialects (excluding Kentish) into Northern, Midland, and Southern is sufficient for taking a broad general view of the language in the days before the Norman Conquest.

The investigation of the differences of dialect in our early documents only dates from 1885, owing to the previous impossibility of obtaining access to these oldest texts.  Before that date, it so happened that nearly all the manuscripts that had been printed or examined were in one and the same dialect, viz. the Southern (or Wessex).  The language employed in these was (somewhat unhappily) named “Anglo-Saxon”; and the very natural mistake was made of supposing that this “Anglo-Saxon” was the sole language (or dialect) which served for all the “Angles” and “Saxons” to be found in the “land of the Angles” or England.  This is the reason why it is desirable to give the more general name of “Old English” to the oldest forms of our language, because this term can be employed collectively, so as to include Northumbrian, Mercian, “Anglo-Saxon” and Kentish under one designation.  The name “Anglo-Saxon” was certainly rather inappropriate, as the speakers of it were mostly Saxons and not Angles at all; which leads up to the paradox that they did not speak “English”; for that, in the extreme literal sense, was the language of the Angles only!  But now that the true relationship of the old dialects is known, it is not uncommon for scholars to speak of the Wessex dialect as “Saxon,” and of the Northumbrian and Mercian dialects as “Anglian”; for the latter are found to have some features in common that differ sharply from those found in “Saxon.”