encyclical (adj.)

in reference to ecclesiastical letters meant for wide circulation (for example, a letter sent by a pope to all bishops), 1640s, from Late Latin encyclicus, from Latin encyclius, from Greek enkyklios "in a circle, circular," from en "in" (see in) + kyklos "circle" (from PIE root *kwel- (1) "revolve, move round"). As a noun, from 1837.