Ring Of Truth

Ring Of Truth

I know what the expression means. I am interested in knowing how it came to be. What does the word 'ring' in any of its various meanings have to do with 'the truth'?

One of the meanings of ring is the sound. At one time, merchants and other people using coins were very happy if a coin, when dropped on, say, a counter, had the proper metallic ring, of ringing sound, indicating that the metal was the right kind, not a base metal. If something has the ring of truth, then it sounds as though it were true. Not much of a guarantee, but there it is.
SS

The difference between glass and crystal can be detected pretty reliably by tapping it to make it ring. Glass is a thud; crystal is musical.

And any metallic percussion instrument, such as a bell, that does not "ring true" is said to give out a "false note".