Smith (2011) suggests that this branch denoted the "waxing half-moon", "construed as a vessel filling with liquid". Noting Schuessler (2007)'s observation that 酉 (yǒu)'s OC pronunciation started with *r-, Smith reconstructs *r-juʔ which would later lost its archaic pre-initial *r-, the same phonological split seen in pairs like 游 (OC) ~ 遊 (OC *ju, “to flow, to roam”) > yóu vs. 流 (OC *r-ju, “flow”) > liú. Smith further supposes that *r-juʔ, is an endoactive derivative of *r-ju "flow" by the suffix *-ʔ, meaning "the flowing stage".
As for 酉 (yǒu)'s association with the chicken, Norman (1985) proposes that Chinese and Thai forms derived from Viet-Muong *rə̆k ~ *ruk, truncated from Proto-Vietic*r-kaː(“chicken”), yet Ferlus (2013) thinks this correspondence unlikely. Possibly, 酉 (yǒu) was arbitrarily associated with the chicken, just like 辰 (chén) with the dragon.