Where does “surfning” come from?

surfning (Swedish) comes from English surfing, from English -ing, from Middle English -ynge, from Old English -ung, from Proto-Germanic -ungō — -ing, -ion. "Forms gerund nouns from verbs.".

Ancestry of “surfning”, step by step

StepLanguageWordMeaning
1Englishsurfingpresent participle of surf; The pastime or sport...
2English-ingUsed to form gerunds, a type of verbal nouns,...
3Middle English-yngeAlternative form of -ing
4Old English-ungforming nouns from verbs, denoting verbal action...
5Proto-Germanic-ungō-ing, -ion. "Forms gerund nouns from verbs."
Every word from Proto-Germanic -ungō
surfning — Etymology, Origin & Word History | Etymology Explorer