When I was a child, the thinking of my relatives was that “…son” was the Norwegian spelling, and “…sen” was Swedish. Then I met some “Larson’s” of Swedish descent, who quite naturally believed the exact opposite. Once I began examining the churchbooks (of Norway), I found that for almost every word, place-name, even Christian name, spelling varied from one document to another. Our ancestral farm of Skurdal, for example, is spelled “Skordal,” “Schurdal,” “Schurdahl,” and others. The first name of the same person could also vary: “Anne” vs. “Ane,” “Niels” vs. “Nels,” etc. etc.
The one consistent spelling, ironically, is the ending of the male patronym: Throughout the period I have studied (1800-1900), it is always “…sen,” never “…son!” In our family, and all others. So how the heck did we get to be Larsons?
My current theory — open to argument — points toward immigration officials. Immigrants were interviewed, and it was the officials who wrote down the names. Indeed, many, perhaps most, of the immigrants themselves were illiterate. The clerks knew, of course, the meaning of the name, and used the English spelling, i.e. the son of Lars was most naturally spelled “Larson.” Anyway, that is my thinking. I welcome your comments.