Why did people doubt this? It doesn’t sound so ridiculous that a Germanic-speaking people would come from Scandinavia, which has a island called Gothland, a province East Gothland and West Gothland, a city called Gothenburg and people called Geats (probably related to Goths).
DNA from unearthed car sized scales proving a giant snake carved the rivers and shape of the land would be something ...
* https://en.wikipedia.org/wiki/Wagyl