Not often used within the meaning of BDSM but sometimes found in context to mean someone who knows a lot about a subject, such as whipping or roping.
Historically, a master craftsman (sometimes called only master) was a member of a guild. In the European guild system, only master craftsmen were allowed to actually be members of the guild. An aspiring master would have to pass through the career chain from apprentice to journeyman before he could be elected to become a master craftsman. He would often have to produce a sum of money and a masterpiece before he could actually join the guild. Becoming a master was often very hard.