子

Pictogram (象形) – an image of a baby, with a large head and spread arms. The legs are wrapped in a blanket. Compare with 了, where the arms are wrapped, and 㜽, in which a lock of hair is visible on top. Compare also 棄 and 毓, in which the image of the baby is reversed upside-down.

The big seal script form is much more elaborate, showing a baby with hair on a head (囟) and arms on the two sides of the body, sitting on a stool (几).

See also the right component of 保.

;child

:From Proto-Sino-Tibetan *tsəʔ (“child”).

:Cognate with 字 (OC *zlɯs, “character; letter”), 慈 (OC *zɯ, “loving; kind”), 滋 (OC *ʔsɯ, “to grow, to breed, to propagate, to bring about, to increase”), 孳 (OC *ʔsɯ, *zɯs, “to breed, to propagate”).

;first earthly branch

:Smith (2011) proposes the first earthly branch had been 甾. Observing that 甾 is closely linked with 緇 (“dark, stained”), 淄 (“murky (water)”), 菑 (zī, “field cleared by burning”) (all pronounced *tsrə), he proposes that initially the first earthly branch 甾 (OC *ts[r]əʔ) had meant "darkened, voided, the darkened stage" and had denoted the new moon phase (ibid.). Meanwhile, 子 (OC tsəʔ) had originated from a Sino-Tibetan root meaning "to come forth" and had denoted the moon's "coming forth" stage (i.e. early waning-gibbous phase) (ibid.).

:Sometime in Warring States period, a change occurred that 子 became the first earthly branch and 巳 (OC *s-ləʔ) filled the void of the sixth earthly branch (Matsumaru, 2015), "due to phonological closeness (combined with the semantic opacity of the Branch terms at later eras)" (Smith, 2011).

:Association with the rat was possibly arbitrary, analogous to how 辰, the fifth earthly branch, was arbitrarily associated with the dragon (Ferlus, 2013).