n. pl. sheaths (shēthz, shēths)
a. A usually close-fitting case or covering for a blade, as of a sword.
b. Any of various similar coverings.
2. Biology An enveloping tubular structure, such as the base of a grass leaf that surrounds the stem or the tissue that encloses a muscle or nerve fiber.
3. A close-fitting dress.
4. A condom.
[Middle English schethe, from Old English scēath; see skei- in the Appendix of Indo-European roots.]
(click for a larger image)sheath
Persian sheath (left) and dagger (right)
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.