From the addition of Chinese 秦 ("Qin") during the Han dynasty to the self-proclaimed title of 始皇帝, from Chinese 始 ("first") + 皇帝 ("emperor"). Owing to the Chinese preference for two- or three-character names, the title was then contracted.
秦始皇 (traditional and simplified, Pinyin)
Although the forms First Emperor, Shi Huangdi, and Shih Huang-ti remain more common in non-scholarly English, 秦始皇 is much more common in modern Chinese, with the non-truncated forms only appearing in scholarly or historical works.
The personal names 嬴正 and the rare hypercorrections 趙正 and 赵正 are anachronisms: Chinese of the period generally employed their 姓 (ancestral names), 氏 (clan names), and 名 (given names) separately and not in the compound form of modern Chinese.