From:10th century, Li Xun (李珣), 《海藥本草》 ([Over]seas Pharmacopoeia)
Lúhuì shēng Bōsīguó, zhuàng sì hēitáng (yítáng), nǎi shùzhī yě.[Pinyin]
Lu-hui grows in the country Po-si [i.e. Persia], has the appearance of black confectionery, and is the sap of a tree.
This is in reference to a blackish-brown, inspissated form of aloe, obtained by boiling its sap down to a mass. This form of aloe was popular in much of Eurasia in antiquity, and was of medicinal value. The 13th-century book Zhu Fan Zhi describes the plant as:
Lu-hui comes from the land of Nu-fa of the Ta-shi country [i.e. Arabia]. It is derived from a vegetable product, which looks like the tail of a king-crab. The natives gather it and pound it with implements made of jadestone, after which it is boiled into an ointment and packed in skin bags, and this is called lu-hui.
The land of Nu-fa corresponds to Dhofar in Southern Arabia, a region historically renowned as a centre for Aloe cultivation.
A common folk etymology interpretation of the word is 盧 (“black”) + 會 (“to assemble; to concentrate”).
During the Edo period, this plant was known in Japan as roe, as an abbreviation of the Latin-derived genus name Aloe.
The kanji spelling is ateji (当て字), based on the borrowed reading of e for 薈(official on'yomi of wai and kai, historical kwai), based on the goon reading of e for separate character 會, the lower portion of the 薈 character (and the traditional form of modern 会). Over time, the irregular e reading reverted to the then-official kwai reading, which then shifted to produce modern rokai.