Is it farther or further?
late 14c., from Old French laxatif (13c.), from Medieval Latin laxativus "loosening," from Latin laxatus, past participle of laxare "loosen," from laxus "loose, lax" (see lax). The noun meaning "a laxative medicine" is from late 14c.
laxative lax·a·tive (lāk'sə-tĭv)
A food or drug that stimulates evacuation of the bowels. adj.
Stimulating evacuation of the bowels.