The names of the Tiangan and Taisui jinian have no meaning in the Chinese language and have long been thought of as renderings of foreign words.
Here are the two groups of names:
Tiangan (Heavenly Stems)
Taisui jinian (Counter Jupiter Stations)
Recently, Wu An-Qi suggested in a Chinese language publication that the Tiangan names were of Daic and Austronesian origin connected with words for body parts, and linguistic remnants of the coastal Dongyi people of early Chinese literature.
Decimal Heavenly Stem cyclical characters are used in concert with the duodecimal Dizhi "Earthly Branches" to count hours, days, years, etc. J. Norman found an Austroasiatic origin for the names of the graphemes used to describe six of the animals associated with the Dizhi branches.
Tiangan characters were among the most frequently seen on Oracle Bone Inscriptions. The ten cyclical characters were associated with the Shang Jia, the ten ancestors of the Shang Dynasty who were worshipped on the respective day of the 10-day Tiangan week.
In earlier times, the Tiangan characters were known as Shi Ri "Ten Suns" and scholars have connected the name with the myths of the Ten Suns of Xihe that rested on the Fusang Tree. Thus, the Ten Suns also stand symbolically for the ten ancestors of the Shang kings.
Shang divination used these cyclical characters to foretell the auspicious nature of the related day in the 10-day week. There is some indication that the 10-day week may also be linked with a base five counting system. The number five occurs frequently in Shang numerology. Most convincingly in the series of artificially-produced cracks in turtle shells and other oracle bones. These cracks were normally five in number and other mirrored on each side of the turtle shell producing a polar set of 10 cracks (Sarah Allan, The Shape of the Turtle: Myth, Art, and Cosmos in Early China, pp. 114-124).
Some submerged ideology from the old divination practices may have survived and given rise to the later division of the Tiangan stems into five yin-yang pairs based on the new doctrine of Five Phases.
In Southeast Asia, the five-day week and to a lesser extent the 10-day week is quite common with the latter also found frequently out into the Pacific. The five-day week was usually a market week and is extremely common in Southeast Asia and also in Africa. The 10-day week can be either a market week or a three-fold division of the lunar month.
Among the Ifugao of northern Luzon, the tengao was a Sabbath-like celebration held at the end of the 10-day week. The ancient Hawaiians had a sacred 10-day taboo period known as anahulu. The Maori and Caroline Islanders divided the lunar month into decades although one week inevitably had to be of nine days. In Kiribati, they had names for movements of the Sun over a 10-day period. The Javanese-Balinese calendar had both the five and ten day weeks incorporated with other time periods in the fascinating 210 day year cycle.
The Taisui jinian system is a more perplexing problem. Although many solutions have been offered for the names of the Counter Jupiter stations, none appear remotely convincing. One suggestion is that the words come from a minority language, possibly from the state of Chu south of the Yangtze during the Warring States period, a language that eventually became extinct.
Paul Kekai Manansala
Norman, J. "A note on the Chinese duodenary cycle." In Linguistics of the Sino-Tibetan Area: the state of the art, Pacific Linguistics C-87, G. Thurgood, JA Matisoff and D. Bradley (cdi), 85—9. Canberra: Australian National University, 1985.
Wu, An-Qi. "A Study of Tiangan（天干）in Chinese and Daic Language," 民族語文 (Ethnic Language) vol. 4, 2005, 6-10.