Write it down
It's a Chinese idiom. Pinyin is Tu ò D ì ch é NGW é n, which means agile thinking. From the miscellany of Yunxian.
The origin of Idioms
Feng Zhi's Yunxian Zaji in the Tang Dynasty has an item of "writing on the spot", praising Li Heyun: "some people pay a visit to Li He, but they don't speak for a long time. Three people spit on the spot, and three people write on the spot."
Idiom usage
Used as a predicate or attributive; used in writing.
Write it down
military orders are like a mountain - jūn lìng rú shān
let the matter be viewed in this light - zuò rú shì guān