Nice to know that I have a good friend who´s interested in my site. Now I'am busy to do more research on the name Posthumus. After presenting the results I'll try to make an english version.
In brief my site tells that my great-grandfather Gerrit Gerrits Posthumus went to the town hall of Workum in Friesland (the Netherlands) and registered himself and his family, in order of the Napolean law of 18 july 1811. He choose the name Posthumus in stead of the second name. He was, as most of the people in Friesland at that time, named after his father: Gerrits = from Gerrit. The name Posthumus in the birthregister of the church was added because his father had died before he was born. To add Posthumus or Postumus was a Frisian custom.Only the nobility in Europe did the same (Slovakia: Ladislaus Posthumus, Heinrich Posthumus in Gera (Germany) and so on).
So in all the towns and villages of Friesland they did the same in 1811, registrating the name Posthumus and less Postumus as a surname. In 1947 after a census in the Netherlands there were in Friesland 821 persons count with the surname Posthumus and none with Postumus.
After 1811 many Frisians emigrated to other provinces of the Netherlands (one of them was my grandfather), to America, South-Africa and other countries, among them off course with the surname Posthumus. Everyone with the name Posthumus who respond to my site had a Frisian ancestor.
Following the line Shakespeare (Leonatus Posthumus in the play Cymbeline), the coin with the emperor of Gaul Postumus and the statue in Bollendorf (Luxembourg) with the name Postumius, you can imagine that there is a Roman connection with the name Posthumus.
The rest of my site shows were the name Posthumus appears and some genealogical information about the ancestors of Nick Posthumus and about my ancestors.