1 and jing are the sounds made in the dropping well.
2. dòng's surname.
"Er" is actually the word "Dan" in Oracle Bone Inscriptions. In ancient times, cinnabar was selected by sinking a well, so this word is a signifier. A little bit in the well symbolizes cinnabar. Unfortunately, Oracle Bone Inscriptions was lost in ancient times and was excavated in modern times for textual research. Therefore, the ancients did not know this word, so this word is a variant of "well", but it is not the case.
Extended data:
Exquisite etymology:
The Chinese word "Zi" originated in Oracle Bone Inscriptions, and Oracle Bone Inscriptions has the word "Zi", or the word "Dan" today, a point in the well, which is the symbol of cinnabar. Because of the word "well", it also refers to well, and the bronze inscription is also commonly used as "shape, shape" and other words. The Eastern Han Dynasty's Shuowen Jiezi, observed from the small seal script, thought it was the initial shape of the well, but actually lost its original intention. As for future generations, it was even more misleading, and I didn't know that it was the word "Dan" in ancient times. Only the pronunciation still retains the Dan sound. It was introduced to Japan in the Tang Dynasty, and later I extended this word to Japan. Imagine it, and it had the meaning of "1: 1". (Actually, the vessel is deep, but a little fear refers to the topping on the rice.)
In Japanese, the word "丼" comes from the Edo period, saying that "ズんどんや" is a shop full of single-serving food, and the bowl used here is called "悭りりけ".
Greed means being stingy and insatiable, so eating "どんぶり" in "けんや" can extend to those who are stingy and full.
It is also explained in the Japanese dictionary that the Chinese character "丼" is the original word of "Jing", which literally means the onomatopoeic word generated when an object is thrown into a deep well. The Chinese writing of "丼" as "どんぶり" in Japanese further indicates the "big bowl".
Reference link: Baidu Encyclopedia-丨