The Smithsonian has a nice article with an overview of the treble clef and how the symbol we know so well came to be.

...So, with apologies to the more musically inclined reader, I looked into the origin of the treble clef and the answer was quite simple. The treble clef, the top symbol you see in the photo above, is also known as the G-clef, which gives you the first clue to its origin.

For more, visit Smithsonian.com. Via a Facebook post by Lauri's List