Many people think that the names of Roman forts in Britain were Latin. Although the country was administered in Latin, just as in Gaul, most fort names are a mix of Latin and the indigenous language.
The fort at Wallsend is a case in point. The Notitia Dignitatum, a record of the military posts of the empire, lists the fort under the section, per lineam Valli (on the line of the Wall):
Tribunus cohortis quartae Lingonum, Segeduno
Tribune of the Fourth Cohort of Lingones Segedvnvm**The Lingones were a Gaulish cavalry regiment.
Segedunum was a critical fort in the military infrastructure of the island. It sits at a perfect apex above the River Tyne looking down two long navigable reaches, almost to the coast in the east and almost to Newcastle in the west.
Regarding Segedunum’s meaning, dun is simply the Celtic for ‘fort’, evidenced in the hundreds of place names containing this word, including the original name for Durham, Dunelm.
While ‘sege’ means power or force, from Proto-Indo-European *segh-. See German sieg meaning ‘victory’, as well ‘siege’ coming from the Old French sege. So the accepted translation of Segedunum is ‘Powerful Fort’, which makes perfect sense.
However, I discovered, to my astonishment, that Romaneranames.uk puts forward the root *seg-₂ meaning mean ‘to attach’ or ‘tack on’ in Proto-Indo-European — see Latin/Italian segue meaning ‘following on’. Is it just a coincidence then, that the largely accepted view among historians is that Segedunum was an afterthought? Originally, Hadrian’s Wall is believed to have ended at Newcastle.
Lots of evidence points to this. Newcastle had a substantial vicus (adjoining civilian settlement). It had key roads meeting there such as Cade’s Road, and was close by the Stanegate, while it seems Pilgrim Street may have led north towards the Devil’s Causeway, which cuts a line through Northumberland. Newcastle also had a bridge that predates the Wall, making it the vital crossing point over the Tyne. It is also possible that there was a thriving pre-Roman village in the Pandon Dene.
With its high promontory beside the Lort Burn, which runs under Dean Street, Newcastle is an obvious place of strength. As well as this, the Vallum, (the rampart running parallel to the Wall on the south side) likely started just west of Newcastle and ran right across the county, but it does not feature east of the city to Wallsend. Most importantly, the section of Wall between Newcastle and Wallsend is narrower than the Wall west of Newcastle, indicating a later date consistent with the width of the Wall in the west of the country.
Presumably the Romans felt the need to extend the Wall to Wallsend in order to prevent raids coming down the Ouseburn valley and elsewhere, and because Wallsend provided such a strategic situation relative to the river, it was viewed as a natural terminus.
So for ‘seg’ to mean ‘attach’ or ‘following’, provides a particularly apt candidate for the fort’s meaning, viz. ‘The Added Fort’. The inherent semantic ambiguity in ‘seg’ was surely not lost on the Romans.