I think it's more about the population displacement. The Romans still didn't move large numbers of their population to Gaul, even if they butchered the Gauls. In Britain this certainly didn't happen, the Gaelic population remained, although the Romans did destroy the druids, famously cleansing the druidic religious centre on Anglesea by killing everyone and burning everything.

The language changed over decades as the upper classes became Romanised (and in the same way Normanised a thousand years later), with Latin/French becoming the courtly language and Gaelic/Saxon the commoner's language. Until finally English emerges as a bastardised combination of all of them.

Whereas in the Danelaw the invaders changed the language and culture in a single generation wherever they took over. Though it's interesting that on the Isle of Man the Viking raiders only killed the men, and settled down on the island with the Manx women, resulting in a Gaelic-speaking Danish culture. There are places in Scotland where this happened too. It's a different combination from the Danelaw, where the settlers brought their own women and the English were displaced completely.

"Britain" is a Romanised corruption of the pre-Roman Gaelic name for the island, "Prydwen". The British identity was already well established before the Romans. They became the "Romano-British" under Roman rule, still speaking Gaelic, and then the Welsh as they were displaced by the incoming Saxons (and still speaking Gaelic!). The Welsh identity is definitely a product of the Saxon invasion, as you say, including the massive still-smouldering resentment of the Saxons (they refer to England as "Lloegyr" which I was told by a Welsh historian means "lost lands" but that doesn't seem to be accurate).

Nit: Gaelic is the wrong word here. They spoke Brittonic. "Gaelic" is "Q Celtic", spoken exclusively at that point in Ireland (and then later by Irish settlers in the north of Britain which became the Scotts).

The Brittonic speakers later became the Welsh, Cornish, and (as emigres to the continent) the Breton.

Very different branches of the Celtic language tree. Not mutually intelligible. Brittonic has more in common with (extinct) Gaulish ("P celtic")

Also the Romans established a landholding system in Gaul that took its agricultural lands under Roman control, so in a sense they definitely had impact on the local population. The rich farmland of Gaul was one of the key reasons for the conquest in the first place.

Though service in the Roman military by Gauls themselves meant they could in turn have rights to access the land as Romans. A further method of Romanization though.

I wasn't going to that level of pedantry, but you're absolutely right :)

I've lived in Dublin, the Isle of Man, and Cardiff - really interesting hearing the language and the differences. I even tried learning Manx Gaelic, but didn't get very far.

I've always wondered how Welsh sounds to Scottish or Irish Gaelic speakers and vice versa. Seems like on paper at least they're a bit further apart than, say, Spanish and French, or Norwegian and German, but not as far apart as, say Russian and Lithuanian. Within the same Celtic language family but phonetically so different as to be difficult to recognize? The P/Q thing seems pretty drastic.

Both also seem to have crazy orthography, too, hard for an English speaker to figure out

I've seen a Welsh and Gaelic speaker try and work it out twice now. It sounds "familiar" but doesn't make any sense either way.

Manx and Irish Gaelic is just-about mutually understandable, though with difficulty. It's like a Londoner trying to understand a Glaswegian.

I gave up trying to learn Gaelic after learning that there are no words for "yes" or "no". To agree with someone you have to construct a positive sentence agreeing with them (e.g. "sure and so it is"). This suddenly made so many Irish-English colloquialisms make sense :)

>and within two or three centuries the Gaulish languages and most cultural practices were extinct.

Gaulish was alive and well during the 5th c. Latin really stuck with the Merovingians.

Interesting, just read more on this. The Jean Manco book ("Blood of the Celts") I had read on this topic seemed to err on an earlier side for the end of spoken Gaulish, but it sounds like some people people believe it may even have lasted into the 9th and 10th centuries (!). Some people even say there's evidence of contact with Breton, which would be neat (I wonder if there'd be some mutual intelligibility between those two, that late!)

* https://www.academia.edu/28555947/ON_THE_GAULISH_INFLUENCE_O...

Gaulish being around in the 9th or 10th centuries is a bit fanciful. As far as I know direct sightings end during the 5th century and circumstantial evidence ends during the 6th c., at the same time Christianity became truly ubiquitous even in remote areas and Latin was solidified as the only cultural language. It makes little sense for Gaulish to have survived much longer.

There's certainly a case to be made for some dialects of Breton having a Gaulish substrate (after all Gallo-Romance languages all have it and that mutation occurred around the time Bretons migrated into Gaul).

Yeah the paper I linked to above is pretty critical about the idea of late attestations of the language generally. Even seems to suggest nothing truly concrete beyond the 3rd century. So leaves it fairly ambivalent about whether there is truly Gaulish influence into Breton.

I find this stuff fascinating :-)