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.
There actually is a reference from Chrysostom as well that would support this idea:
[W]hile sin and disobedience had not yet come on the scene, they were clad in that glory from above which caused them no shame. But after the breaking of the law, then entered the scene both shame and awareness of their nakedness. (Louth, Conti and Oden, Ancient Christian Commentary on Scripture: Old Testament I, Genesis 1-11 2001, 72)
I asked about the sudden feeling of being ashamed of being naked in Biblical Hermeneutics when asking about Genesis 2 and 3 - Why was nudity suddenly a shame for Adam [and Eve]?.
The following is the accepted answer and has biblical references which may help with your question.
In Genesis, why did Adam and Eve become ashamed when they realized they were naked after eating from the Tree of the Knowledge of Good and Evil?
The Tree of Knowledge was Knowledge of BOTH Righteousness AND Evil:
NKJV, James 4:17 - Therefore, to him who knows to do good and does not do it, to him it is sin.
It was not revelation of some sin that they had done that made them ashamed.
But rather, it was knowing the "Good" that they had not clothed themselves in, that made them ashamed, (the "Good" imitation of the love and mercy of God - righteousness).
At the very least, even if the narrative isn't teaching to clothe oneself in "good work" or "righteousness", then it is at least affirming that clothing your body is a "Good" thing.
So, compared with the goodness of God - they were likely ashamed of how their own "goodness" measured up to God's own.
NKJV - Revelation 3:15-18 - “I know your works, that you are neither cold nor hot. ... 18 I counsel you to buy from Me gold refined in the fire, that you may be rich; and white garments, that you may be clothed, that the shame of your nakedness may not be revealed; and anoint your eyes with eye salve, that you may see.
Although Scripture might speak to "modesty", Scripture elsewhere affirms nudity - "before the Lord".
Scripture shows justification for more extreme, and public, displays of nudity:
NKJV, 1 Samuel 19:24 - And he also stripped off his clothes and prophesied before Samuel in like manner, and lay down naked all that day and all that night. Therefore they say, “Is Saul also among the prophets?”
NKJV, 2 Samuel 6:20-21 - ... And Michal the daughter of Saul came out to meet David, and said, “How glorious was the king ... uncovering himself ... as one of the base fellows shamelessly uncovers himself!” 21 So David said to Michal, “It was before the Lord ...
In Scripture, "Garments" Are Metaphorical for "Works", BOTH Righteousness AND Evil:
NKJV, Isaiah 59:6 - Their webs will not become garments, Nor will they cover themselves with their works; Their works are works of iniquity, And the act of violence is in their hands.
NASB, Isaiah 61:10 - I will greatly rejoice in the Lord, My soul shall be joyful in my God; For He has clothed me with the garments of salvation, He has covered me with the robe of righteousness, As a bridegroom decks himself with ornaments, And as a bride adorns herself with her jewels.
NKJV, Daniel 7:9 - “I watched till thrones were put in place, And the Ancient of Days was seated; His garment was white as snow, And the hair of His head was like pure wool. His throne was a fiery flame, Its wheels a burning fire;
People are NOT "spiritually naked" - when they do evil:
Note: This is an objection to another answer that asserts that nakedness is a metaphor for sinfulness - but even "sinful people" are "clothed".
NKJV, Zechariah 3:4 - Then He answered and spoke to those who stood before Him, saying, “Take away the filthy garments from him.” And to him He said, “See, I have removed your iniquity from you, and I will clothe you with rich robes.”
Adam and Eve, (like infants), were in a unique situation: they were neither clothed in goodness, nor evil. Although they had disobeyed God, this text seems to show that their disobedience was not on the same level of "evil / filthy garments".
