Breaking down each word it means thousand autumns.
Why does this mean a playground swing?
Is this a local cantonese word or is it used in mandarin too?
in 唐 dynasty (618-907), there're records of 千秋:
the peom 樓前 by 王建
天寶年前勤政樓 每年三日作千秋 飛龍老馬曾教舞 聞著音聲總舉頭
another one is the 漢武帝後庭鞦韆賦 by 高無際, which stated:
況鞦韆者﹒千秋也﹒ 漢武祈千秋之壽﹒ 故後宮多鞦韆之樂
later, in 記纂淵海 卷八十九, by 潘自牧 (~1195) of 宋 dynasty (p33-34 of pdf file);
that the term "鞦韆" was elaborated. mr 潘 claimed that, according to mr 高:
鞦韆﹒漢武帝後庭之戲﹒ 本云千秋﹒祝壽之詞也﹒ 語訛轉為秋千﹒後人乃旁加革
briefly, it's 千秋 --> 秋千 --> 鞦韆
back to the original question, the game "swing" in cantonese is "千秋", which share the meaning "thousand autumn", a term for wishing for longevity.
lastly, i would say that it's one of the numerous evidences, that cantonese is highly correlated with middle chinese. or, one might say that cantonese preserve more / change less than other "dialects".
have fun :)
Hong Kong Cantonese call playground swing "韆鞦". (we consider 鞦韆 / 秋千 a Mandarin term )
cau1 cin1 (jyutping)
qiu1 qian1 (pinyin)
In Hong Kong, 韆鞦 is often written as 千秋 by people who either didn't know the correct characters or just want to use characters that have less stokes.
We can tell from the context of a sentence that we are talking about "swing" or "thousand autumns".
In the process of simplifying Chinese characters, there are rare words that simplified wholely, so each character cannot be considered as the simplified version of the corresponding origin character in this case. For example, the word 衚衕 is simplified to 胡同, 鞦韆 is simplified to 秋千, that means in this case, the characters 胡 is not the simplified characters of 衚, the characters 同 is not the simplified characters of 衕, the characters 鞦 is not the simplified characters of 秋, and the characters 韆 is not the simplified characters of 千. 千秋 may mean thousand autumns literally, it is always the same form from ancient times to now. But if the word 千秋 is another name of a swing (秋千/鞦韆) in some dialect, it should written as 韆鞦 in traditional Chinese.