I prefer the term copperhead.
Pennsylvania was originally settled by Scandinavians but by 1701 they'd been driven out of Lancaster County by Quakers and were re-established in York County, or they moved South to Western and North Central Maryland.
Over the next 100 years that core area expanded West leaving a vast population of people with Norse surnames and no idea about how that happened.
No doubt some ante bellum Doughfaces did transmogrify into para bellum Copperheads.
But the vast majority saw the error and joined the Union cause.