Though the etymology is unrelated, this is the name of a mountain on the island of Crete where, according to Greek myth, the god Zeus was born.
Kahlan was likely created as a variant of Kaylyn, given the pronunciation. Whether usage of the name is due to the character, or whether the variation is just another in the progression of spelling variants naturally created by parents from the popular Kaylyn, is unknown.
This name has been borne by six kings of Sweden, including the 16th-century Gustav I Vasa. Another notable bearer was the Austrian painter Gustav Klimt (1862-1918).