Inventing stupid words for “weak” people like that is an ancient German running gag. Like Schattenparker (someone who parks in the shade) or Warmduscher (someone who likes warm showers). It’s always tongue-in-cheek and no serious insult.
I’m German too and we totally used Mäusespeck in the 80s/90s. I guess you’re just younger, today people know what marshmallows are (and speak better English in general).
Inventing stupid words for “weak” people like that is an ancient German running gag. Like Schattenparker (someone who parks in the shade) or Warmduscher (someone who likes warm showers). It’s always tongue-in-cheek and no serious insult.