Kerstgen is a Dutch, Finnish and Scottish based name meaning "Christian" in English or in German "Christmas". Also in Dutch spelled Kerstiaen, Kerstecen or Kersteken. Kerstgen's origin is predominately a male Dutch/Finnish name, but has several spellings and variations throughout the world as a predominately female name.
The name is found in the 16th century Dutch history as a famous Dutch warrior. It is also still found in the south-east of The Netherlands, a province called Limburg. It is indeed a masculine name in The Netherlands, while googling Dutch pages with this name I did come across some prominent people in the 16th century with this name.
Dutch male names 1393-1396
"Kerstgen" means Christian warrior, strong, assertive, compulsive, organized, intelligent, leader, sensitive, relentless, good-hearted, helpful, protective, fierce