From the 13th century the term master had come to mean one who had progressed in skill so far in their trade that the master of his guild had accepted his work as being of very high quality as to exceed that of a journeyman. He was permitted to take apprentices of his own and train them to be journeyman in turn.
Masters in the SCA
Master is the title (actually an honorific) given in the SCA to those who are members of the Order of the Pelican and/or Order of the Laurel. Women who hold the title may use the title Mistress.
A member of the Order of Chivalry who has declined to swear fealty is referred to as a Master-at-arms, and styled "Master" rather than "Sir".
It is also the term used for some SCA ministers or officers, e.g. Kingdom Lists Officers are sometimes referred to as Masters of the Lists.