What does this particular unique surname GUSTAFSON mean? Origin of surname GUSTAFSON?? Is GUSTAFSON really common surname like Smith??

Gustafson is the surname of my 6 footer 4 tall male friend for my whole life time since I was kid. I googled the origin of his surname GUSTAFSON, ancestry website shows me that it's both swedish, Norwegian and Danish etc... I am not sure if Gustafson is Norwegian name or Swedish name...
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