This is the 6568th most frequent Swedish word.
melwin
"Melwin" is a Swedish given name, derived from Old English meaning "friend of justice" or associated with pleasant qualities; it has no direct dictionary definition.
The word 'Melwin' here is being used as a proper noun, specifically as the name of a person.
Melwin älskar att spela gitarr.
Melwin loves to play the guitar.
The word 'Melwin' is used as a possessive form (Melwins) to indicate ownership or association, in context indicating that it is Melwin's turn.
Var det Melwins tur att spela nästa låt?
Was it Melwin's turn to play the next song?
Here, 'Melwin' is used as a proper noun, given as the name of a subject in a descriptive context.