The Migration Period is called the Migration Period namely due to the Germanic tribes mass migrations. Celts, Scythians, Picts, and Teutons are all irrelevant to it, as Merlkir said.
Goths (Ostrogoth or Visigoth...or their respective predecessors the Greuthingi and Thurvingi), Vandals, Franks, Saxons, Langobards (Lombards), Burgundi, Alemanni (successor to the Suebi tribes, such as the Marcomanni), Rugi, etc...are what he is looking for. The Norse, with the possible exception of the Rugi (debated origin) did not attack the Roman Empire directly. However, many of the previous tribes were said to come from Scandinavian areas (as all Germans are said to), though namely the Goths, Burgundi, and Vandals.
As for the source being from the 1700's, yes it is. That doesn't mean it is irrelevant to read. The famous Herr Grimm of Grimm brothers' fame wrote a book series on old Germanic words, culture and languages and it must be the most thorough thing I have ever read too (dry as hell though). I can't imagine it being any more detailed. He was fluent in probably a dozen of old Germanic languages and runic alphabets.
Merlkir, to be honest, I don't care if new people have changed their views on various sources since that time. In several decades those views will change too. What I care about is straight information, what happened after the Battle of Adrianople, for example. We know the Goths then began a pillaging raid throughout much of Greece. Those sort of facts are what I care about when I read history books, not what some ******* thinks is why they attacked one city over another. From such dry facts I make my own sense of it, and I think I do a better job of it than ancalimon (though that is like saying I play better football than a man without legs).
Anyway, as I said it is a classic. I will get the titles of Grimm's books too, though I don't know how you might get your hands on a copy. I own a copy of them, but they were not easy to get.
Tacitus's Germania is excellent too, though it was written a couple centuries before the migrations (around the time of the Marcomanni Wars).
