sheath

Definitions

General English

Construction

Electronics

  • A protective covering, case, or enclosure, especially for a blade or blade-like object.
  • A protective outer covering for a cable. Depending on the intended use for the cable, and the operational environment, it may protect against moisture, abrasion, magnetic fields, radiation, and so on. Some cables have more than one sheath. Also called cable jacket, or cable sheath.
  • In a gas tube, a layer of electrons which surrounds the anode when its current is high. Also called anode sheath.

Medical

  • noun a layer of tissue which surrounds a muscle or a bundle of nerve fibres

Origin & History of “sheath”

A sheath is probably etymologically a ‘split stick’. The word comes from a prehistoric Germanic *skaithiz, which also produced German scheide, Dutch schede, and Danish skede. this seems to have been derived from the base *skaith ‘divide, split’ (source also of English shed ‘give off, drop’ and ski), in which case the notion underlying it would have been of a stick split open so that a sword blade could be inserted into it.
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