For Lennartz there are 245 on Yasni with different names.
Among the most common last names on Yasni Lennartz is on position 4367.
In my family there was an old uncle who has studied genealogy. By him following interpretation Lennartz> Lennart comes (or Lennert and similar spellings)> Leonard (Leonhard and u sim. STATIONE. / Holland and Skandianvien)> Lionard (and similar. STATIONE.) Lionheart (England) and so led he branch of our namesake easily ended up on Richard the Lionheart in England, although our (by that uncle created) pedigree in the High Middle Ages in two French Catholic clergy.