1560s, from Kasper Schwenkfeld (1490-1561), Silesian Protestant mystic who founded the sect. Their original name for themselves was Confessors of the Glory of Christ. Schwenkfelder (n.) is attested from 1882.
They select their ministers by lot, maintain a strict church discipline, and do not observe the sacraments. They are now found chiefly in Pennsylvania. [Century Dictionary, 1890]