conclave (n.)

late 14c., "a place where cardinals meet to elect a pope," also "the assembly of cardinals to elect a pope," from Italian conclave, from Latin conclave "a private room, chamber suite," probably originally "a room which may be locked," from assimilated form of com "with, together" (see con-) + clavis "a key" (from PIE root *klau- "hook"). Extended sense of "any private assembly" is by 1560s.