serpent's-tongue

from The Century Dictionary.

• noun A fern of the genus Ophioglossum, especially O. vulgatum, so called from the form of its fronds; adder's-tongue. See cut under Ophioglossum.
• noun A name given to the fossil teeth of a species of shark, because they show resemblance to tongues with their roots.
• noun A name given to a short sword or dagger whose blade is divided into two points, especially a variety of the Indian kuttar.