Pastor (n.)
1242, "shepherd," also "spiritual guide, shepherd of souls" (1377), from O.Fr. pastur "herdsman, shepherd" (12c.), from L. pastorem (nom. pastor) "shepherd," from pastus, pp. of pascere "to lead to pasture, graze," from PIE base *pa- "to tend, keep, pasture, feed, guard" (see food). The spiritual sense was in Church L. (cf. Gregory's "Cura Pastoralis"). The verb in the Christian sense is from 1872.
source