I heard quite often Korean people say "[약방의 감초](http://endic.naver.com/krenIdiom.nhn?sLn=kr&idiomId=7ccda0146fab414688b9862761df7c4f&query=%EC%95%BD%EB%B0%A9%EC%9D%98+%EA%B0%90%EC%B4%88)" which literally translates to "licorice (root) of drugstore (pharmacy)" to refer to a person or thing that is indispensable. 

Where does this proverb come from and what does it mean exactly? Does it have a negative connotation?