Mao Zedong led China for a long time, from the establishment of the People's Republic in 1949 to his death in 1976. Everyone spells his name "Mao Zedong". But if you look at contemporary sources talking about him, his name is spelled "Mao Tsetung" or even "Mao Tse-tung". Why did Mao change his name?
The answer is that his name didn't change at all.note What changed was romanization of the Chinese Language.
Rendering Chinese in the Roman alphabet is tricky for several reasons, among them being that Chinese uses a number of sounds not found in English or indeed any other European language. The romanization system has changed several times to try and account for that. The problem is that you have to figure out what to prioritize and keep track with actual changes in pronunciation by native speakers. The other problem is that there is more than one "Chinese language" — the one we all refer to as "Chinese" is Mandarin Chinese, and most romanization systems are based on how the language is spoken in Beijing.
Pinyin and Wade-Giles
The most famous change is from the Wade-Giles system to the Pinyin (literally "spelled sound") system, which is responsible for the transition from "Mao Tsetung" to "Mao Zedong". Wade-Giles was named for the two British diplomats who developed it at the end of the 19th century, whereas Pinyin was developed by the PRC government in the 1950s. Wade-Giles was designed to approximate English pronunciation, whereas Pinyin was designed to assign a distinct letter to every sound in Chinese, even if it doesn't exactly correspond to what the letter represents in English. To use Mao's name as an example:
- Wade-Giles has a "ts" where Pinyin has a "z". It's actually pronounced closer to "ts", but Chinese has two "ts" sounds that are not exactly the same. Pinyin deals with this by assigning them different letters ("z" and "c"), whereas Wade-Giles gives them both "ts" and tells you to deal with it. Pinyin actually has four different letter combos ("ch", "zh", "j", and "q") which correspond to "ch" (or "ch'") in Wade-Giles.
- Wade-Giles has a "t" where Pinyin has a "d". It's pronounced closer to a "t", but without the aspiration — English speakers have a tendency to exhale hard at the end of most of their consonants, almost like they're saying "h" at the same time. They do it without even recognizing it — if you want an unaspirated consonant, imagine the accent of a ridiculously posh South African. Chinese distinguishes between the aspirated and unaspirated consonants, but Wade-Giles has "t" for unaspirated and "t'" for aspirated, whereas Pinyin has "d" for unaspirated and "t" for aspirated (using the English "voicing" distinction).
- Wade-Giles has "ung" while Pinyin has "ong". in Chinese it's actually pronounced with the "oo" in "book" — the systems can't agree on how to render it, so there you go. (That's why Kung Fu is gongfu in Pinyin.)
None of this takes into account the tones. Chinese is a tonal language — the pitch you give a syllable can change the meaning of that syllable. English doesn't have a great way of denoting it. Wade-Giles basically gave up, although there was a brief push in the 1920s for "Gwoyeu Romatzyh", which would have added random letters to Wade-Giles syllables to denote the tones. Pinyin uses actual accent marks (hence "Máo Zédōng").
One thing you might be wondering is how Beijing got such a drastic change from "Peking" — Wade-Giles would render it as "Peiching". That's because many place names in China historically used the even older Chinese Postal Map Romanization, which is based on names Europeans gave to these places in the 16th and 17th centuries, which in turn came from pronunciations in Min, Cantonese, Hakka, and now long-forgotten southern dialects of Mandarin. This can be seen fairly consistently in some places; modern Nanjing was known as Nanking, and modern Jilong was known as Keelong. In others, it's damn arbitrary, such as rendering Guangzhou as "Canton" based on the pronunciation in the local variant of Yue Chinese, which became known as Cantonese after this name of the city. (Except that's not what they called the city, but the entire province, known in Pinyin as Guangdong.)
This now brings us to the other Chinese languages, each of which may have their own romanization standard. This is seen most often with Cantonese, being as it is the local language in longtime British colony Hong Kong. Cantonese has two competing standards, Yale and Jyutping — they're fairly similar, but the latter includes numbers at the end of syllables to indicate tones (and there are even more in Cantonese than in Mandarin). Hong Kong and Macau use Cantonese as an official language, so names are romanized directly from Cantonese. However, outside these areas, such names are often given the Mandarin pronuncation of the characters and romanized in pinyin. For example, Wong Kar-wai is pronounced Wáng Jiāwèi in Mandarin, and Chinese areas not speaking Cantonese will most likely romanize his name as such. Another example is Hokkien, a southern Min language spoken in parts of Taiwan, often rendered in Pe̍h-ōe-jī.
Why the change?
Pinyin was born out of the PRC government needing to change things. Part of it was politics — the Communists had had enough of British intervention in China and weren't going to let them dictate how their language was written in English. But part of it was a practical matter — Chinese characters are complicated, and it was a daunting task to try and teach them to a billion people. There was an actual push to dump Chinese characters altogether and either make a new alphabet (like Korean did when they invented Hangul in the 15th century) or use an existing Western alphabet (like what Vietnamese did — it uses Latin characters). The Chinese toyed with the idea of using the Cyrillic alphabet like their Communist neighbors in the Soviet Union. But in the end, they decided against entirely getting rid of the Chinese character set, instead adopting a simplified version of it.
Sometimes people look at Pinyin and think it was invented to make it easier to input on a computer, but the system was developed in the 1950s and 1960s, well before computers were ever a thing in Communist China. (Look, Mao famously used a rotary phone well into the 1970s — why would they have cared about computers?)
Unfortunately, as with anything involving Communist China, things got politicized pretty quickly. The PRC government touted Pinyin as the definitive, super-special-awesome way to romanize Chinese, and by the late 1970s, most things in Chinese — including Mao's name — had been converted to Pinyin spelling. Other places, however, were more reluctant to change over.
Taiwan was very reluctant to follow the PRC's lead for obvious reasons and held onto Wade-Giles for the longest time. It's obvious in the names of their cities (Taipei instead of "Taibei", Kaohsiung instead of "Gaoxiong") as well as "Kuomintang" instead of "Guomindang". However, they do more or less speak the same Mandarin as the mainlanders, and there was a push to adopt Pinyin in the Republic of China as well. They used a variant called Tongyong Pinyin from 2002 to 2008 before giving up and switching to the official PRC Hanyu Pinyin. But throughout Taiwan, there's a stubborn refusal to abandon Wade-Giles, and there are also substantial numbers of Hokkien speakers who use their own romanization as well.
Much of the Chinese diaspora of the 19th century spoke non-Mandarin languages, and that can be reflected in the romanizations you see today. Many a Friendly Local Chinatown has names rendered in ways that made you think the locals were making fun of them, but part of it comes from those immigrants not speaking the same Chinese we see today; San Francisco's Chinatown in particular was largely populated with Cantonese speakers, which gives the city an unusual link to Hong Kong (for a non-Commonwealth city anyway). Singapore and Malaysia are unusual cases in that they still hang on to Wade-Giles, perhaps owing to the large numbers of Hokkien speakers there and their status as former British colonies (even as Singapore adopted the PRC's simplified characters — their relationship with China is complicated).