Source : Webster's Revised Unabridged Dictionary (1913)

Catnip \Cat"nip`\, Catmint \Cat"mint`\, n. (Bot.)
   A well-know plant of the genus {Nepeta} ({N. Cataria}),
   somewhat like mint, having a string scent, and sometimes used
   in medicine. It is so called because cats have a peculiar
   fondness for it.