Smith's Bible Dictionary
Key. The key of a native Oriental lock is a piece of wood, from seven inches to two feet in length, fitted with the wires or short nails, which, being inserted laterally into the hollow bolt which serves as a lock, raises other pins within the staple so as to allow the bolt to be drawn back.
(Keys were sometimes of bronze or iron, and so large that one was as much as a man could carry. They are used in Scripture as a symbol of authority and power. Giving keys to a person signifies the intrusting of him with an important charge. Matthew 16:19. In England, in modern times, certain officers of the government receive, at their induction into office, a golden key. - Editor).
These files are public domain.
Smith, William, Dr. Entry for 'Key'. Smith's Bible Dictionary. https://www.studylight.org/dictionaries/eng/sbd/k/key.html. 1901.