The soybean (Glycine max) is credited with having provided Chinese civilization with an abundant source of protein, but considering that it is “the world’s foremost oilseed source” and that is “is widely used as cooking oil“, the primary reason behind its domestication may have been its high content in oil.
Soybean is called 荏菽 MC nyimX syuwk in ode 245〈大雅･生民〉of the Shi Jing:
Legge’s translation of this passage:
“He fell to planting large beans.
The beans grew luxuriantly”
Legge’s “large beans” is 大豆, the common appellation of soya beans in Chinese culture. The Mao commentary on the Shi Jing states that 荏菽 is the same thing as 茙菽, which was presumably how that thing was called when the Mao commentary was written. Zheng Xuan’s 鄭玄 (127-200) Maoshi jian 毛詩箋, a commentary on the Mao commentary, adds that both 荏菽 and 茙菽 refer to 大豆— the soybean. So we have two ancient names for the soybean: in MC pronunciation, nyimX syuwk and nyung syuwk.
In a forthcoming paper, Ma Kun and I present evidence of a dialectal difference in Western Zhou times, manifested in particular in the treatment of the Old Chinese *-um rhyme: in western Old Chinese, *-um changes to *-uŋ, while in eastern OC, it changes to *-əm. Middle Chinese continues eastern OC, with *-əm further evolving to MC -im after nonpharyngealized onsets. Western OC words also find their way into a limited layer of Middle Chinese: 茙 nyuwng and 荏 nyimX clearly form a doublet, western and eastern, of an OC *num(ʔ). We may reconstruct an early OC form *num(ʔ)-s-t(ʰ)uk, where *s-t(ʰ)uk means ‘bean’ and *num(ʔ) is its modifier. What did *num(ʔ) mean ?
Not ‘Glycine max’. 荏 MC nyimX also refers to 蘇, the plant Perilla, another source of oil. This suggests that *num(ʔ) was a name of vegetal oil in OC. I propose that 荏菽 and its western doublet 茙菽 originally meant ‘the oil bean’.
A number of western ST languages have a word num or similar to express the meaning ‘oil’: Tibetan snum, and similar forms in Lepcha, Cuona Menba, Boka’er. Chinese *num(ʔ) and these western ST forms are evidently cognate.
There is no linguistic evidence to suggest that the soybean was a Sino-Tibetan domesticate, although it may have been used as a source of oil.