1. This clan name appears in the Records of the Grand Historian written by Sima Qian. Apparently, the First Emperor (father of the Second Emperor) being born in the State of Zhao where his father was an hostage, he later adopted Zhao as his clan name (in ancient China clan names often changed from generation to generation), but this is not totally sure.
2. Based on ancient China naming patterns, we can infer that Qin was the clan name of the royal house of the State of Qin, derived from the name of the state. Other branches of the Ying ancestral family, enfeoffed in other states, had other clan names. Qin was thus possibly also the clan name of the Second Emperor.
3. The royal house of Qin did not carry the practice of temple names, which were not used anymore since the establishment of the Zhou Dynasty, so the Second Emperor does not have a temple name per se. However, his official name "Second Emperor" can somehow be assimilated to a temple name, being the name under which the emperor would have been honored in the temple of the ancestors of the dynasty.
4. Posthumous names were abolished in 221 BC by the First Emperor who deemed them inappropriate and contrary to filial piety.
Qin Er Shi was the son of Qin Shi Huang (the First Emperor of Qin), but he was not the original crown prince. In 210 BC, he accompanied his father on a trip to Eastern China, during which trip his father died suddenly. Under the advice of the chief eunuch Zhao Gao and prime minister Li Si, he forged a fake decree of his father, which ordered his brother, the heir Fusu, to commit suicide and appointed himself to be the heir.
As emperor, he was not able to contend with nationwide rebels. He depended on Zhao Gao so much that he himself acted like a puppet emperor. In 207 BC, the Qin dynasty was on the brink of collapse and Zhao Gao was afraid that Qin Er Shi would ask him to take the blame. Therefore Zhao Gao and others teamed up to force the emperor to commit suicide.
A son of Fusu, Ziying, was made king of Qin by Zhao Gao. Ziying soon killed Zhao Gao and surrendered to Liu Bang one year later.
Qin ErShi (229 BC - beginning October 207 BC), literally Second Emperor of Qin Dynasty, personal name Huhai, was emperor of the Qin Dynasty in China from 210 BC until 207 BC.
Qin ErShi was the son of Qin Shi Huang (the First Emperor of Qin), but he was not the original crown prince.
In 207 BC, the Qin dynasty was on the brink of collapse and Zhao Gao was afraid that Qin ErShi would ask him to take the blame.
Qin Shi Huang (秦始皇) (November or December 260 BC-September 10, 210 BC), personal name Zheng, was king of the Chinese State of Qin from 247 BC to 221 BC, and then the first emperor of a unified China from 221 BC to 210 BC, ruling under the name First Emperor.
Qin Shi Huang continued military expansion during his reign, annexing regions to the south (what is now Guangdong province was penetrated by Chinese armies for the first time) and fighting nomadic tribes to the north and northwest.
It was during Qin ErShi's "rule" that powerful families came to war, with the strongest of them rising to power and bringing order back to the land, thus starting the next dynasty of emperors.