In a comment on a post of Guillaume Jacques’s I cited the word 袁 yuán ‘long robe’ as being cognate with Tibetan གོན་ gon “clothing”. This drew a response from Guillaume, from which I extract these passages:
“l’étymologie avec 袁 est difficilement acceptable philologiquement: la glose que tu cites « long robe » est la traduction de celle du shuowen 长衣貌, mais ce mot supposé est sans attestation textuelle (无书证); les dictionnaires ne citent que les gloses de dictionnaires: http://www.guoxuedashi.com/kangxi/pic.php?f=gxhz&p=2055”
and:
“Je pense que l’on ne peut pas utiliser de mots dont l’existence même n’est pas assurée pour faire du comparatisme (en plus quand bien même il aurait existé, la glose X貌 suggère qu’il devait plutôt s’agir d’un idéophone, pas d’un nom).”
Real words do not always occur in the received literature; for instance the Cantonese and Hakka popular word for “egg” has no early Chinese text occurrences, yet it corresponds well to the word “egg” in other ST languages (Baxter and Sagart 2014:324).
Specifically with regard to 袁:
The same word appears written as 褑 and 褤 in the Ji Yun 集韻 with the spelling 于元切= hjwon，and the gloss 衣也 “clothing”. The Ji Yun here is not citing the Shuo Wen, since the characters and the gloss wording are different.
The Shuo Wen itself which says “袁, 长衣貌也” is not citing an earlier dictionary/word list either, since there is no earlier attestation of the character, and the Shuo Wen is the first Chinese dictionary.
Dialectally the word is attested. Huang Kan 黄侃 in his《蕲春语》wrote that a long robe is called 長褑 in his own dialect, noting that the word must be the same as 褑 in the Ji Yun.
Although there are no early text examples of 袁, the character is attested both paleographically and as the head of a phonetic series. It includes 衣 “clothing” and a hand.
There is, then, no reason to assume that 袁 is not a real word. The comparison to WT gon is not problematic.
references
Baxter, William H. and Laurent Sagart. 2014. Old Chinese: a new reconstruction. New York: Oxford University Press.