The progenitor of the Groblers and Grobbelaars in South Africa was Jan Grobler, who as Dutchified to Jan Grobbelaar. According to thw Geslacht-Register der Oude Kaapsche Familiën (Villiers, 1884-1893): “De stamvader van deze familie was Jan Grobbelaar, gehuwd met Geertruida Knoetzen”. More recent genealogical sources give the ancestor as Johann Grobler as reported in (Malherbe, 1966) and (Grobler, 1987). This is apparently incorrect. Dr. Paul Grobbelaar makes a convincing argument (Grobbelaar, 2012) based on a handwriting analysis of Jan Grobler’s signature that the progenitor’s name was Jan and not Johann (see Appendix A).
Post script: The first name Jan is not common in Germany. As a matter of interest, I looked through the Tangermünde – and surrounding area – church books available on microfilm (although dating from the 1800’s and thus not necessarily relevant to the 17th and 18th centuries). The first name Johann is very common. The name is sometimes written Johan – about 1 out of 50 times I would estimate. I did not see a single entry for a Jan. This may imply that Jan Grobler or his predecessors were recent immigrants to Germany – say within 1 to 4 generations. Jan is currently very popular as a male first name in the Czech Republic and Poland, so perhaps it indicates an origin from one of these countries. Furthermore, I did not see any Grobler records in the Tangermünde or Grobleben church books, but I found some Groblers in the Tangerhütte church books.