The term also appears in a charter of Æthelstan, king of the English. It appears in several variant forms (brytenwalda, bretenanwealda, &c.), and means most probably "lord of the Britons" or "lord of Britain"; for although the derivation of the word is uncertain, its earlier syllable seems to be cognate with the words Briton and Britannia; but Kemble derives Bretwalda from the Old English word breotan, to distribute, and translates it "widely ruling."
The first recorded use of the term comes from a West Saxon Chronicle of the late 9th century applying the term to Ecgberht, who was King of Wessex from 802-839. The chronicler also wrote down the names of seven kings Bede had listed in his Historia ecclesiastica gentis Anglorum in 731.
There is no evidence that the term bretwalda was a title that had any practical use, or even any existence before the ninth-century chronicler. Bede wrote in Latin and never used the term, and his list of kings holding imperium should be treated with great caution, not least in that he overlooks kings such as Penda of Mercia who clearly held some kind of dominance in their time. Similarly, in his list of Bretwaldas, the West Saxon chronicler ignores Mercian kings such as Offa. It is unlikely that there was a succession and defined duties, and it is doubtful whether the term Bretwalda is anything more than a later simplification of a complex structure of kingship. Problems arise when historians take the term and infer from it something that was not there.
Bretwalda is, therefore, a highly problematic term, and one which, if anything, was merely the attempt by a West Saxon chronicler to make some claim of West Saxon kings to the whole of Great Britain. This shows that the concept of the unity of Britain was at least recognised in the period, whatever was meant by the term. Quite possibly it was only a survival of a Roman concept of "Britain"; it is significant that, while the hyperbolic inscriptions on coins and titles in charters often include the title rex Britanniae, when England was actually unified the title used was rex Angulsaxonum, king of the Anglo-Saxons.
Over the later twentieth century this assumption was increasingly challenged. In 1991, Steven Fanning argued, "It is unlikely that the term ever existed as a title or was in common usage in Anglo-Saxon England. The fact that Bede never mentioned a special title for the kings in his list implies that he was unaware of one. In 1995 Simon Keynes wrote, "if Bede's concept of the Southumbrian overlord, and the chronicler's concept of the 'Bretwalda', are to be regarded as artificial constructs, which have no validity outside the context of the literary works in which they appear, we are released from the assumptions about political development which they seem to involve...we might ask whether kings in the eighth and ninth centuries were quite so obsessed with the establishment of a pan-Southumbrian state.
Thus, more recent interpretations view the bretwaldaship as a complex concept. It is now recognized as an important indicator of how a ninth-century chronicler interpreted history and tried to insert the West Saxon kings, who were rapidly expanding their power at the time, into that history.