The full version of the jingle "Cherry with small mouth and willow leaf eyebrow" is
Liu Yemei, almond eyes, cherry with small mouth.
The source of the allusion of Cherry Mouth:
"Bai Shangshu (Bai Juyi)" Fan Su, a concubine, is good at singing, and Xiaoman, a prostitute, is good at dancing. He wrote a poem: "Cherry Fan Sukou, Yangliu" Xiaoman's waist."
Bai Juyi's poem explains: Mei Ji Fan Su's mouth is small and bright, like a cherry; Xiaoman's waist is weak and slender, like a willow.
-----"Poetry on Poem and Reflections on Things" by Meng Qi of the Tang Dynasty