late 14c., purgatif, in medicine, "having the property of cleansing by expelling impure matter from the body," from Old French purgatif (14c.) and directly from Late Latin purgativus, from purgat-, past-participle stem of Latin purgare "to cleanse, purify" (see purge (v.)). The noun is attested from early 15c., "a medicine that evacuates the intestines" (Old English medical texts have clænsungdrenc).
word-forming element meaning "drug, medicine," also "poison," from Latinized form of Greek pharmakon "drug, poison" (see pharmacy).
in old medicine, "pertaining to the humors of the body," early 15c., from Old French humoral (14c.), from Latin humor (see humor (n.)).
also repellant, 1660s, "agent or medicine that reduces tumors," from repellent (adj.). As "substance that repels insects," 1908.
c. 1600, "a medicine made of secret ingredients by secret methods," but commonly "quack medicine," from Latin nostrum remedium "our remedy" (or some similar phrase), presumably indicating "prepared by the person offering it," from Latin nostrum, neuter of noster "our," from nos "we," from PIE *nes- (2); see us. In extended use, "a pet scheme for accomplishing something" (1749).