witness

Definitions

General English

  • noun a person who sees something happen or who is present when something happens
  • noun a person who is present when someone signs a document
  • verb to be present when something happens, and see it happening

Commerce

  • verb to sign (a document) to show that you guarantee that the other signatures on it are genuine

Law

  • noun somebody who sees something happen or who is present when something happens
  • noun somebody who appears in court to give evidence

Origin & History of “witness”

Witness originally meant ‘knowledge’ or ‘wisdom’; it was simply an abstract noun formed from wit. this was extended via ‘knowledge gained by observation’ to ‘testimony’ in the Old English period, and by the beginning of the middle English period ‘person who gives testimony’ was well established.
http://www.dictionarycentral.com/definition/witness.html