A word made out of the misspelling of the Swedish term "Fredagsmys".
Fredagsmus can be translated into Fridaypussy or a weekend vagina.
It's when a woman gets fresh and clean, preferebly waxed, downstairs, because it's Friday and she wants to party and hook up with some hot dude.
If the woman dances to much, and get all sweaty she could destroy her fredagsmus (Fridaypussy) and get a discomuff (discopussy) instead.
I have a fredagsmus and I'm ready for a night out!
It's always good to be prepared with a fredagsmus.