Where does the name ‘Chongqing’ come from?
Let’s look at the historical origin of the name, and then discuss the two Chinese characters of ‘Chong’ and ‘Qing.’
First of all, I would like to quote from the Lonely Planet on the origins of the name.
Chongqing means ‘double happiness’ or ‘repeated good luck.’ It was originally named Gongzhou but Emperor Zhaodun of the Song Dynasty renamed it in 1190 when he ascended to the throne. As he had been previously made the prince of the city, he called it Chongqing in celebration of these two happy events.
The Chinese characters in ‘Chongqing’ 重庆
重 is a polyphonic character, meaning that there are multiple ways of pronouncing it, depending on how it is used.
Here are the results you get from entering the characters into Baidu Translate.
（重量； 分量） weight
（重视） lay [place, put] stress on; place value upon; attach importance to
heavy; serious; weighty; deep
（加重） heavily; severely
The first way of pronouncing 重 is ‘zhong’ as a falling tone. It can be a noun, verb, adjective or adverb, but is generally associated with weight, seriousness or emphasis.
（重复） repeat; duplicate
（重新； 再一次） again; once more
（姓氏） a surname
As ‘Chong’ with a rising tone, it has the meaning of the verb ‘repeat,’ the adverb of ‘again,’ the quantifier ‘layer,’ and can possible be a Chinese surname.
It is this ‘Chong’ used in the name Chongqing, to mean ‘repeated.’
（庆祝；庆贺） celebrate; congratulate
celebration; occasion for celebration; a surname
‘Qing’ with a failling tone is a verb meaning to celebrate or congratulate.
Putting these two words together, it should be clearer how the name 重庆 means repeated or double celebration.