Florent is a form of Florence or Florenz from the southern Netherlands.
Gosewin is a form of Goswijn, a compound name which goes back to Germanic roots meaning "Goth" (the ancient Germanic tribe) and "friend".
Gerlof goes back to Germanic roots meaning "spear" and "wolf".
Claes would be an alternative spelling of Klaes, a Frisian short form of Nicholas.
Renger goes back to a compound Germanic name from regin, "advice, counsel" and ger, "spear".
The above information all comes from Woordenboek van Voornamen by J. Van der Schaar.