Adam and Eve Clothed in Light Before the Fall - Origin of this belief? I've stumbled multiple times across the claim that Adam and Eve were clothed in light before the fall, and afterward they saw their nakedess not merely as a new form of enlightenment ("Suddenly I feel like I should put on some clothes!") but rather visual change had occurred. 

What original sources contain this information to make it such that some commonly believe this?
It seems this interpretative tradition goes back millennia to the ancient Jews. BioLogos has a short article on the development of the tradition that Adam and Eve "wore" garments of light, attributing it to the Jewish squeamishness regarding the naked body, then exacerbated by Greek culture, rampant with nudity, flooding the Jewish populations at the time of Alexander the Great.

The article does not list any ancient Jewish sources as having discussed this topic, but it does mention and quote one Christian: Ephraem, the 4th century Syrian theologian. The most revealing quote is:


  It is because of the glory with which they were clothed that they were not ashamed. When it was taken away from them—after they had violated the commandment—they were indeed ashamed, because they were now naked (Commentary on Genesis, 2:14). [Other quotes are offered in the article]


In a different vein of "study", nearly 1500 years later, Blessed Anne Catherine Emmerich had an extensive and very vivid personal revelation in which she described Adam and Eve as clothed in light.


  They were like two unspeakably noble and beautiful children, perfectly luminous. and clothed with beams of light as with a veil. From Adam's mouth I saw issuing a broad stream of glittering light, and upon his forehead was an expression of great majesty. Around his mouth played a sunbeam, but there was none around Eve's. I saw Adam's heart very much the same as in men of the present day, but his breast was surrounded by rays of light. In the middle of his heart, I saw a sparkling halo of glory. [More at Shield of Faith]


The LDS even have their own take on it, as presented in Meridian Magazine. The Nakedness and the Clothing of Adam and Eve is a very well sourced article on the topic, though it is centered around LDS theology, which you may not be looking for. Again there doesn't seem to be any ancient Jewish sources quoted, but many other sources that make the claim are cited. For example:


  Rabbinical tradition taught that, following his transgression, “Adam. lost his [heavenly] clothing-God stripped it off him,”15 and similarly that Eve “was stripped of the righteousness in which [she] had been clothed.”16 


The most common explanation and defense for the belief is multifaceted. First, God is clothed in light; his Shekinah. This radiant glory of God shines though in the most righteous, like it did when Moses came down from Mount Sinai. Similarly, Adam and Eve, in the image of God, radiated God's glory. Second, some, Jews particularly, argued that the Garden was a very holy place. In fact, the most holy of places. And Adam was a priest of sorts. Since God required his priests to be ornately clothed while in the tabernacle, Adam likewise must have been clothed.

There are multiple reasons why a Christian would believe this and there are multiple sources with different motivations seemingly conceiving it independently. I personally do not find the origin of this idea the main component in its continued adherence throughout the ages.