Is it ensure, insure, or assure?
"of or pertaining to shepherds," early 15c., from Old French pastoral (13c.), from Latin pastoralis "of herdsmen, of shepherds," from pastor (see pastor (n.)). The noun sense of "poem dealing with country life generally" is from 1580s.
A work of art that celebrates the cultivated enjoyment of the countryside. The poem “The Passionate Shepherd to His Love,” by Christopher Marlowe, is a pastoral. Its first stanza reads:
Come live with me, and be my love;
And we will all the pleasures prove
That hills and valleys, dales and fields,
Woods or steepy mountain yields.