杞憂 (Kiyū)

Literally: Worry of Qi - fear that the sky might fall

Example: “雨の心配は杞憂に終わり、運動会は晴天だった。” — Our worry about rain was borrowing trouble; sports day was sunny.

English equivalent: To borrow trouble

Origin: Drawn directly from a story in the Chinese philosophical text Liezi, specifically its opening chapter, Tianrui: a man from the small state of Qi became so consumed with worry that the sky might collapse or the earth might crumble beneath him that he lost his sleep and appetite entirely, tormented by a catastrophe with no real prospect of happening. The four-character idiom qǐ rén yōu tiān — "a man of Qi worries about the sky" — was later shortened simply to "杞憂," using "Qi" together with "worry" to name the whole story in two characters. Qi itself was a real, if minor, state in what is now Henan province, established when King Wu of the Zhou dynasty appointed a descendant of the earlier Xia dynasty's King Yu to rule it and carry his line's traditions forward — giving the idiom's setting a genuine, if historically obscure, home.