I’ve been studying and researching a lot about 5th century Britain. In the History of the kings of Britain by Geoffrey of Monmouth, written in the 12th century. After Hengist betrays him at the treachery of the long knives, Vortigern flees and meets a child, Merlin. After a while, Merlin has a prophecy which goes on for a long time, but it starts with two dragons fighting. A white one and a red. Signifying the Saxons and the Britons.
So originally I understand this was in Latin so they were ‘draco’? But Vortigern and Merlin would have spoke in an old Brittonic language, and as I understand Dragon was ‘wyrm’. Wyrm also used to mean a lot of crawling things like snakes and others.
My question is. Is it possible that over the course of Ambrosius Merlinus having his prophecies(if he ever did)in the 5th century. To Geoffrey writing the accounts down, 700 years later, that there was a mistranslation and that the dragons Merlin saw, were actually some form of snake, or slow worm?
I understand that these prophecies are most likely all made up, because they have so much accuracy as to what is to come. With Uther and his brother coming back to kill Vortigern.
You're right to suspect that there are some complicated layers of translation here, and that the creatures in the story may not always have been "dragons" in our modern understanding of the term. However, I'd caution against assuming that this tale refers to a historical event involving physical creatures of any kind. The earliest account appears some four hundred years after the confrontation at Dinas Emrys supposedly took place, and Merlin[us] doesn't get involved until Geoffrey of Monmouth's famous version, another three hundred years after that.
The oldest version of the tale appears in the Historia Brittonum (“History of the Britains”), a Latin text written in northern Wales, probably 820’s, possibly by a monk named Nennius (though this last bit is controversial). The HB may have been composed as a British counter-narrative to Bede’s Historia ecclesiastica gentis Anglorum, which is about a century older and makes no mention of Vortigern encountering mythical creatures. All in all, the story that the HB tells here is fairly similar to Geoffrey’s better-known account, which makes sense--the HB was almost certainly one of Geoffrey’s principal sources. But there are some crucial differences.
The prophetic child, for instance, is not Geoffrey’s Merlin[us], but rather “Ambrosius.” The HB probably takes this name from Gildas’s De Excidio et Conquestu Britanniae, in which Ambrosius is a valiant general of Roman descent who seemingly lived two or three generations before the writing of De Excidio. Gildas has nothing to say about Ambrosius’s childhood, other than that his parents were some sort of imperial or post-imperial officials (they “wore the purple”) and that they died in the upheavals of the post-Roman period. The HB explicitly makes Ambrosius’s father a consul--but only after the boy is designated as a sacrificially-potent child “born without a father,” which may indicate that the HB is mashing together a few different accounts here. And the creatures unearthed beneath the building site (here located at “Heremus,” somewhere in Gwynedd) are vermes—”worm,” “serpent,” and “vermin” are all possible translations. While the vermes don’t seem to be of extraordinary size, Ambrosius explains that they form part of a symbolic tableau. The pool they’re found in represents the world, the tent covering them represents Guorthigirn’s [Vortigern’s] kingdom, and the two vermes represent two dracones, which in turn are totems for the native Britons and the Saxon invaders. This triple analogy—vermes=dracones=gentes—is pretty unusual, and may again suggest that the HB is collapsing or synthesizing a few different stories.
Geoffrey of Monmouth’s Historia Regum Brittaniae, completed sometime in the mid-1130’s, reworks older materials like the HB into a wild, prophetically-driven, and largely fantastical narrative. Though written in Latin, like the HB, its initial audience were not the Welsh but rather the Anglo-Norman nobility (though it was quickly adopted by the Welsh in the various receptions of Brut y Brenhinedd). While Geoffrey has plenty to say about the character he calls Aurelius Ambrosius--corresponding to Gildas’s Ambrosius Aurelianus and the HB’s Ambrosius—he transfers the tale of the prophetic child and the reptiles to a new character, Merlinus. (Though he does gesture to his sources, stating that Merlinus “was also called Ambrosius.”) Many aspects of Geoffrey’s Merlinus seems to derive from an entirely different character, Myrddin Wyllt (“Myrddin the Wild/Mad”), a legendary poet associated with the area around the modern Anglo-Scottish border. Other indications suggest that Myrddin Wyllt was believed to have lived in the late sixth century, nearly a hundred and fifty years after the time of Vortigern. But Geoffrey seems to have taken a particular interest in this character, and made him integral to a wide, ahistorical swathe of the British past. Geoffrey’s Merlinus is very much “born without a father”—he’s the child of an “incubos,” a part-human, part-angel spirit of the lower heavens that strives to mate with mortal women. And there’s nothing about vermes in the HRB—Geoffrey, never one to avoid the fantastic, makes the subterranean creatures explicitly dracones. (He also turns the boy’s one-sentence prediction from the HB into nine pages of baroque prophecy, which was often detached and treated as a separate work from the HRB as a whole).
The third text that deserves a mention here is the Welsh Cyfranc Lludd a Llefelys (“Tale of Lludd and Llefelys”). This appears as a supplement in one of the Welsh translations of HRB that I referenced above, but it might contain elements of a supplemental tradition. Set in the ancient pre-Roman past, it provides a backstory for how exactly the two prophecy-creatures ended up in an underground pool in Gwynedd. In terms that may be an attempt to make sense of the HB’s confusing set of analogies, Lludd a Llefelys explains that the beasts are shape-changing dragons (dreigeu, a Welsh borrowing from Latin), who conduct aerial combat in the shape of aruthter aniueileit (“dreadful animals”) but, when tired, plummet back to earth as [p]archell[od] (“piglets”[!]). In this harmless/adorable form, they are finally trapped and buried on the future site of DInas Emrys.
So yes—the forms of the creatures in this tale do shift around quite a bit. But even the earliest version is clearly legendary, and later accounts only get more fantastical from there.
*Also, just to note that wyrm is Old English, not the Celtic Brittonic language that [some theoretical historical equivalent of] Vortigern and Ambrosius would have spoken in addition to Latin. “Dragon” is Welsh is draig, with the Geiriadur Prifysgol Cymru postulating a Brittonic form *drakī; snake is neidr (no postulated Brittonic form from GPC, unfortunately, though there’s an Old Cornish form nader) or sarff (also from Latin, serpens). Ifor Williams thinks that the vermes of the HB are a translation from the Welsh pryf, which derives from the same Proto-Indo-European root as vermes/wyrm and means “vermin, little wild creature”--which may or may not explain the piglets of CLaL.
Note that dragons in ancient and early medieval art are often very serpent-like in form, and the words used for them in several languages (wyrm, drakon) also meant snake (or more specifically, big snake). Note also that in many legends, dragons were as likely to have a poisonous bite or breath as they were to breathe fire.
So I think the question "did they mean Dragon, or did they mean snake?" is possibly not a distinction they would actually have made. What they were thinking of was probably in essence "big, dangerous, snake-like monster, probably with magic powers".