The existence of viking in the World of Wizarding in the Wild West is basically boiled down to one character, and was the result of his passionate and immovable insistence in revitalizing, even restoring the traditions of his people.
He had been marooned on a mysterious island many years earlier by his crew.
But since the strange island had a funny way of playing with people's perceptions of time, he had no way of knowing that centuries of time had passed. When Mortimer found him in the 1840's, he assumed that it had only been a decade or two, and indicated as much. But what he soon learned was that it had been over 500 years, and that the entirety of the civilization he had known was now gone.
He mourned for their loss. He mourned for those he knew and loved, and that he would never see again. But what he felt most of all was the loss of his identity; the culture he had known and loved was gone from this earth, and would never be experienced by anyone else ever again.
Or so he thought at the time. As he grew to accept the sad reality he was now bound to, he began to share memories and thoughts. It was after hearing another one of his stories that his friend, traveling buddy, and only confidant Mortimer suggested to him that perhaps he could bring back some of the traditions he missed so much.
It was then that an idea was planted that would bear fruit a number of years later.
He would go on to find a new wife who would bear many sons and daughters to him in time, and he would go on to teach them the viking ways, and customs, and many of the traditions, stories, and folklore that he had been raised with as a boy. Only this time, he would omit the less savory parts of his past life, preferring to incorporate the higher alchemical philosophies and patterns that he had learned more recently from his friend who had saved him from that strange and lonely island so many years ago, and that he had involuntarily spent so many years of his life on.
And so, it was through the influence of this sole survivor of this lost northern people that there came a revitalization of the culture and people we know today as the vikings.