Every step a fuckin' adventure.

Remember when he, Jarl, and their party were scaling the Wall, part of it gave way and they fell to their doom? Him.
His son, Sigorn, becomes Magnar after Styr's death.

"Ayo, lesson here, Dunn. You come at the King, you best not miss."

I'll put it in baby's terms: O' = Irish.

Yep, you're spot on! That's going waaay back.

Let me state it as simply as I can then:

O'anything is nearly always Irish.