Jensen is a very common ln in Denmark. I've never heard of Jenson, looks like a mix-up of Janson and Jensen to me.
The reason that these names (Jensen, Jansson, Jönsson, Johansson, Jonsson, Johnson, Jackson) are so common is that the fn John (or Johan, Jan, Jon, Jens, Jöns, Jack) always has been very common.
All son-names are kind of boring imo. Many Swedes change their dull son-ln to a more uncommon one. Which is why I can't understand why people want to use such names as fn.
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