The buoyant, funky, finger-clicking synthpop track, written by 27-year-old Icelander Daði Freyr Pétursson (it’s pronounced “Dathi”) has multiple ingredients that add up to a viral smash.

Daði’s wife and inspiration for 10 Years, Árný Fjóla, is one of the members of Gagnamagnið. His sister, Sigrún Birna Pétursdóttir, undertakes backing vocal duties and friends Hulda Kristín ...