Roots of this word have to do straightforwardly with shining and may derive from a pre-Germanic root ghlid- which relates to the Greek word for luxury!  The OED entry for this word – to shine brightly but flickeringly – includes this example from Samuel Johnson.

1784   Johnson Let. 2 Oct. (1994) IV. 413   All is not gold that glitters, as we have been often told.

Ahem.  Yes, we have often been told, Mr. Johnson.  And that wise saying may have morphed over time.  But that’s a different story.

• 08.059 in rockets of glittering sparks
• 13.042 Their glittering mail they had covered again
• 14.023 his belly glittered white with sparkling fires of gems

“glitter, v.” OED Online. Oxford University Press, June 2015. Web. 26 July 2015.