“ It is from this application of the word to these levers in musical instruments that the term is also used of the parts pressed by the finger in typewriters and in telegraphic instruments.
A key is the insignia of the office of chamberlain in a royal household (see Chamberlain and Lord Chamberlain) . The “power of the keys” (clavium potestas) in ecclesiastical usage represents the authority given by Christ to Peter by the words, “I will give unto thee the keys of the kingdom of heaven” (Matt. xvi. 19) . ”