Son of Ragnar

Used to describe someone, regardless to their gender, who is, indeed, a true son of Ragnar.
Such persons are greatly smart, strong and capable in all ways, but mostly they're cunning and sly, thus resulting in their victory over all others. They might be regarded as somehow arrogant, yet they don't act out of greed or viciousness, nor they want to make fun of others. Their deeds are to please the mighty gods, in order be accepted into Valhalla or Folkvangr.

Sometimes it is just used as an interjection.

George: Dudes, y'all seen the last episode of Superstore yesterday?
Carol: OMG yes, Garrett was such a son of Ragnar.

-----other context-----

Jim: is taking a shower
Shampoo bottle: falls
Jim: SON OF RAGNAR!