What is a meaning of suffix "nip" in "Catnip"? [closed]

Catnip comes from cat + nip, where nip comes from nepte. Here nepte is the Old English name of catnip or of a family of herbs including catnip, and originally comes from Latin nepeta (with the same meaning).

Reference: Etymonline

As @peter-shor's answer says already : nip [...] comes from Latin nepeta [...] family of herbs. Regarding the source of the nepeta genus, quoting Floral Centric [...] by William Darlington in 1826:

Same Nepeta genus root (ie. the ancient Etruscan city) is quoted in David Gledhill's The Names of Plants:

Nepeta the Latin name, from Nepi, Italy