mys·ter·y 2 
(mĭstə-rē)
(mĭstə-rē)n. pl. mys·ter·ies
Archaic
Archaic
1. A trade or occupation.
2. A guild, as of merchants or artisans.
[Middle English misterie, from Medieval Latin misterium, alteration (influenced by Latin mystērium, secret rite) of Latin ministerium, from minister, assistant, servant; see mei-2 in the Appendix of Indo-European roots.]