This family was founded was Herman Kolthoff from Kultenhof Estate, Danish Duchy of Slesvig (now Kaltenhof, Schleswig-Holstein, Germany), who had several sons that went on to fame across Europe. They are best known for the Kalthoff repeater - a rapid fire repeating rifle that could deliver 20-30 rounds/minute in the 1650s. Signed examples of their guns can be found in Windsor Castle, Danish Armory Collection, Kremlin Armory Collection.
Descendants
The Kalthoff name spelling name was recorded as Kaldtoft, Kalthof, Kaltof, Kaltoft, Koldtoft according to local pronunciation and spelling habits. All of the families with these names in Scandinavia are descendants. The original seed Kalthoff in each country shared the "Hermansen" name indicating a common father, was famous for advance metallurgic skills (iron manufacturing, advance steel formula for repeating rifles, etc.), and were born within a decade of each other. Kalthoff is a single family-name.