Origins of Northmen?

[Zaru]

Upon viewing my own Haplogroup and Subclade (L21*) as well as Stevo's L21 Project, I notice that the potential trajectories seem to point Northward. The Normans, Scottish, Irish, varieties of English, Manx, Germans, et al seem to have a northern historical connection that precedes their own. Even the Sicilians have a Northern heritage! So, this begs the question- where did the Northmen come from prior to, and have the dna doors been opened in terms of deciphering that question?

Cheers, Rosario