Meaning A boy's name of Swedish origin, it means "sea of bitterness." Origin of Willelmus Swedish , Scandinavian +-100%Zoom level changed to 1 Popular Middle Names Pronunciation 🔊 Listen Willelmus Similar Names Marice Kalle Kjell Kristofer Patrik Edvard Eugen Jonam Maklolm Roald Year by Year Popularity of Willelmus