There has been a tendency in the past to link the Dark Age kingdom name Rheged with the Romano-British period polis of the Novantae tribe, RERIGONIUM. According to Rivet and Smith’s “The Place-Names of Roman Britain”, Rerigonium should be seen as “a latinization of British *ro-rigonio- ‘very royal (place)’. Under their entry for the place-name Regulbium, the authors cite British *ro- ‘great’ (a prefix… rendered in Latin as heard or adapted by Latin speakers, re-, a common prefix). –rigonio- is from British *rig- *rigon ‘king’ with *-io- derivational suffix.
For a full discussion of what past authorities have surmised in regards to the location of Rheged and its possible etymology, see pp. xxxviii-xlii in Sir Ifor Williams' edition of THE POEMS OF TALIESIN.
In my opinion, Rheged is rather easily derived from a Welsh ged, ‘gift’, and the Re-/Rhe- can again be accounted for if we allow the original Ro- to have been altered due to Roman influence. The meaning would be something like ‘Great Gift’ and may have been formed, originally, after the model provided by nearby Rerigonium.
It would be nice to suggest that Ptolemy made a mistake, and his Rerigonium should instead be something like *Rereconion, *re-rec- meaning 'great gift'. Welsh rheg, like ged, means ‘gift.’ Rerec[onion] would exactly match my proposed meaning for Reged. Unfortunately, we are not justified in assuming that Ptolemy made such an error.
Alternately, Rheged could be from rheg (from Brth. *-rek). The -ed is likely the Welsh suffix -ed1. From the standpoint of the philologist, relying on rheg- is a better bet than requiring the *ro- to become *re-. Regularly, we would expect Ro + ged to become Rhyged (I have this confirmed from Dr. Simon Rodway of The University of Wales). According to Professor Koch in CELTIC CULTURE: A HISTORICAL ENCYCLOPEDIA, "The name [Rheged] is Celtic and is related to Welsh rheg ‘gift’, explaining the artful poetic theme of its rulers’ renowned generosity." I would agree with Koch on the etymology, but not on its application as a kingdom name.
We must remember that Urien is linked to Modron and Mabon. Lochmaben is near the Annan, which is thought to derive from a goddess name like the Irish Anu, which has the same root as the Welsh word anaw. One of the meanings of anaw is 'gift.' The Lochmaben Stone is on the other side of the Annan near Gretna Green. The great Burnwark hillfort is nearby and this is believed to have been the oppidum of the Novantae.
From the GPC:
[H. Wydd. anae, yr e. lleoedd Brth. a Gal. Anava, yr e. prs. Gal. Anavos; cf. yr e. prs. H. Gym. Anaugen, Anauoc, yr e. prs. H. Grn. Anaoc, Anaudat, a’r e. prs. H. Lyd. Anaugen]
eg. a hefyd gyda grym ansoddeiriol.
Cyfoeth, golud, budd, rhodd, trysor, hefyd yn ffig.:
wealth, riches, benefit, gift, treasure, also fig.
Perhaps the nucleus of Rheged was found on the Annan? This tribe may possibly be descended from the Roman period Anavionenses, thought to be a sub-group of the Novantae. I would guess that the 'Anna' found at the head of the Men of the North genealogies is for the Annan. She is the wife of Beli, father of Afallach. This is the same Afallach made the father of Modron, wife of Urien. I have no doubt this Afallach is intended as the eponym for the Aballava Roman fort which lies only a half dozen kilometers south of the Lochmaben Stone.
This does leave open the problem of the small Dunragit hillfort near Stranraer and the Rhinns of Galloway. If Rheged refers to the River Annan, why do we find an apparent Rheged name so far to the west? My guess is that at some point the kingdom name Rheged was wrongly identified with Rerigonium. As such, Dunragit as a place-name may be fairly recent. The other polis of the Novantae mentioned by Ptolemy is Leukopibia or, rather, Leucovia, which has been identified with the Roman fort at Glenlochar. However, the Water of Luce quite close to Dunragit makes for a much better Leucovia.
Before closing, I should refer the interested reader to my recent identification of Urien with Uther Pendragon: