Meaning

noun a secret unauthorized meeting for religious worship

noun a building for religious assembly (especially Nonconformists, e.g., Quakers)

originFrom Late Middle English conventicle, conventicule (“a gathering, meeting (especially a secret or unlawful one); (derogatory) a church”), from Latin conventiculum (“assembly; meeting (or the place involved); association”), from conventus (“assembled, convened”) + -culum (suffix forming noun diminutives), perfect passive participle of conveniō (“to assemble, convene, meet together”), from con-…

Etymology from Wiktionary, CC BY-SA 3.0