Sheath /(?)/

Sheath

n.
  1. A case for the reception of a sword, hunting knife, or other long and slender instrument; a scabbard.
    The dead knight's sword out of his sheath he drew.
  2. Any sheathlike covering, organ, or part. (Bot.)

Phrases & Compounds
Medullary sheath
See under Medullary.
Primitive sheath
See Neurilemma.
Sheath knife
a knife with a fixed blade, carried in a sheath.
Sheath of Schwann
See Schwann's sheath.