The four Chinese seasons: 春夏秋冬 are not related to season names in other Sino-Tibetan languages. They are probably innovations of the Chinese branch. This post links to four others where their etymologies are discussed:
zhēng yuè 正月 ‘first month’ and the stop/nasal alternation in Old Chinese codas.
One of the sources of the alternation between stop and nasal codas—the ‘陽入對轉’ of traditional Chinese phonology—is assimilation of a final stop to the nasal initial of the following word. An example is the expression zhēng yuè 正月 ‘first month of the lunar year’. The earliest secure occurrence of 正月 I am aware of, referring to the first month, is in the Luan Shu Fou 䜌書缶, a Zhou bronze inscription:「正月季春元日」’on the first day of the first month’. Palaeographers would probably know earlier ones. The character 正 normally writes *teŋ-s > tsyeng > zhèng ‘correct (adj., v.)’. How did it become used to express the meaning ‘first’ ?
There is in Western Sino-Tibetan (a.k.a. ‘Tibeto-Burman’) a root for ‘one’ which the STEDT website reconstructs as
#2726 PTB *tyak ⪤ *g-t(y)ik ONE (provisional).
The corresponding Chinese root reconstructs as *tek ‘single, only, only one’. It includes these words:
隻 *tek > tsyek > zhī ‘single’ 1260c, 適 *s-tek > syek > shì ‘only’ 0877s, 啻 *s-tek-s > syeH > shì ‘only’ 0877k.
Root *tek and the root in 正 *teŋ-s differ only in the nasality of the coda. This suggests 正 writes 隻 *tek ‘1’ in a context where its ending had become nasalized. The onset of the following word: 月 *[ŋ]ʷat is likely where nasality comes from. 正月 was an appropriate way of putting *teŋ-ŋʷat < *tek-ŋʷat into readable form.
Liu Shiru. 1965. Weijin Nanbei chao liangci yanjiu (Studies on Classifiers in Wei-Jin and Nan-Bei dynasties). Beijing: Zhonghua.
Chinese 秋 ‘autumn’: time of collecting.
The Chinese name of the autumn: 秋 *tsʰiw > tshjuw > qiū ‘autumn; crop’ is relatable to 揫 *[dz]iw > dzjuw > jiū ‘collect, bring together (K)’. We may have to emend [dz]iw to m-tsʰiw (although Mandarin jiū suggests *m-tsiw). There are other cases of alternation between aspirated and non-aspirated stops/affricates in related words.
Chinese 冬 ‘winter’: finish, end of the year’s agricultural cycle.
冬 *tˤuŋ > towng > dōng ‘winter’ is clearly related to 終 *tuŋ > tsyuwng > zhōng ‘end’. An external cognate is Chepang tyuŋh ‘at end’; ‘be weak, exhausted’. Final *-m in various TB languages may be due to assimilation to a verbal suffix -ma, as in Limbu (Michailovsky) tum-ma (√tums-) ‘to be mature, to be ripe’ (of person, grain or fruit). Forms of this verb with final -m, without the suffix, are Jingpo chatum ‘end, finish’; Proto-Ao a-thəm ‘end, finish’ (Bruhn 14). Along with tyuŋh ‘at end’, Chepang has doublet ending in -m: dyumʔ– ‘at ease after completing work’, dyum ‘terminate, reach end’; ‘at end’. This would be the ‘end’ of the year’s agricultural cyle.
Although OC *-um goes to *-uŋ in western China in early OC, we can be sure that *-uŋ in 冬 is not the western reading of an OC *-um word: if it was, it would end up as *-əm in the easter pronunciation ancestral to MC (Ma and Sagart, forthcoming) and we would have MC *-om or *-im. So *-uŋ > *-um in TB is due to a labial suffix.
Chinese 夏 ‘summer’: time of leisure ?
Baxter-Sagart 2014 reconstruct 夏 *[g]ˤraʔ > haeH > xià ‘summer’ (~ *[g]ˤraʔ-s). A homophone is 暇 *[g]ˤra-s > haeH > xià ‘leisure’, with a probable cognate in Written Burmese: â ‘vacant, free; disengaged’. In the two or three months it takes the millets to grow, set ears and ripen, between early summer and harvesting in late summer or autumn, a period of (relative) calm sets in. It would make sense if that period was called ‘leisure’: that would later become the name of summer.
Chinese 春 ‘spring’: beginning of the egg-laying season?
The etymology of Chinese 春 ‘spring’ has always intrigued me… Baxter and Sagart (2014) reconstruct 春 *tʰun > tsyhwin > chūn ‘springtime’. The observation that the phonetic in excavated texts is 屯 *dˤun 0427a goes back to Yu Xingwu (Jiang Yubin 2018). Baxter and I might as well have reconstructed *-u[n] because -r is possible: GSR 0427 contains several likely *-r words.
Baxter and Sagart (2014:324) argue that there was in OC a vulgar word for ‘egg’, different from 蛋 and 卵, for which no Chinese character exists: OC *tʰu[n]. It is only attested dialectally: Cantonese tʃʰœn A1, Hakka tʃʰun A1. The word is vulgar because, at least in Cantonese, it also refers to the testicles, but it is also vulgar in the sense of ‘popular’. It was probably not part of the speech of early Chinese literati. For that reason it lacks a character.
Here again, final -n is ambiguous for -r. The word is a homophone of 春 *tʰun > tsyhwin > chūn ‘springtime’. Assuming the ending was *-r rather than *-n, the word exhibits the Sino-Tibetan sound correspondence OC *-ur, Bodo -əy, Lushai -ui, -Proto-Karen *-ej, WT *-u, matching the PTB word for ‘egg’ in Benedict’s Conspectus (1972): *twiy=twəy.
|Written Tibetan||Boro (Bhat)||Lushai (Lorrain)||Proto-Karen (Luang.)||OC (B-S)||PST (tentative)|
|n.a.||dəy ‘egg’||tui ‘egg’||Ɂdej B ‘egg’||tʰu[r] ‘egg’||#tʰur|
|chu ‘water’||dəy ‘water, river’||tui ‘water’||thej A ‘water’||s.turʔ ‘river, water’||#s-turʔ|
|mchu ‘lip’||(gusu)təy ‘lip’||(not cognate)||n.a.||sə.dur ‘lip’||#m-tur|
There is a connection between eggs and the Chinese new year season. In general birds “will nest and lay eggs during the warmer months in the north [of the US, LS]. Typically, the timeline ranges between early spring and late summer” (here). Late winter or spring is the time that hens (at least those presumably old varieties that do not lay eggs year-round) start laying eggs. One US site (here) reports that
“One of our employees who’s at a mid-latitude in the US reports that any girls [hens, LS] who stop laying during the winter begin again regularly–and surprisingly precisely–on February 1 or 2, about halfway between the winter solstice and the spring equinox.”
I wonder if the Chinese name of spring is not etymologically “when hens start laying eggs” again after the winter interruption. This would be a time worth recording for early Chinese farmers who raised chickens. The mid-latitude US date for the onset of egg-laying corresponds well with the Chinese New Year: “the first day of Chinese New Year begins on the new moon that appears between 21 January and 20 February” (Wikipedia: here).
If valid, this etymology implies that hen-keeping was widespread at the time of the ‘egg’ > ‘spring’ semantic shift, although this may be before the Old Chinese period, perhaps well before.
Addendum Feb 22, 2023: Ma Kun 马坤 points out a paper by Jiang Yubin 蔣玉斌 where the palaeography of 春 is described. The oracle bone graph has 屯 phonetic and clumps of growing grass as signific. No graphical chickens or eggs to be seen ! But considering that ‘egg’ in the language of literati was probably 卵, that the presence of the meaning ‘testicle’ made *tʰu[r] an unpalatable association, and perhaps also that the semantic link between springtime and eggs was not necessarily obvious to upper-class city dwellers, it is not overly surprising that an association with eggs is not apparent in the oldest known form of 春.
Finally, a question: don’t New Year yuanxiao 元宵 (here) look like eggs ?
Benedict (1972) Sino-Tibetan: a conspectus. Cambridge University Press.
蔣玉斌 Jiang Yubin (2018) 释甲骨文金文的“蠢”兼论相关问题。 复旦学报 2018，5：118-138.