一筹莫展
yī choú mò zhǎn · HSK 7
to be at wits' end
一筹 = one plan + 莫展 = cannot unfold: not a single scheme can be spread out
筹 is a bamboo counting-stick used to tally strategies; 展 means to unfold or lay open. 一筹莫展 literally says you cannot unfold even one plan, so every option stays stuck and you are at wits' end.
一 — single horizontal stroke
一 is one of the simplest pictographs in Chinese, depicting a single horizontal line to represent the number one. It has retained essentially the same form since oracle bone script over 3,000 years ago. By extension it also means 'first,' 'whole,' or 'same.'
筹 — bamboo radical 竹 + 壽 (longevity, phonetic)
Originally written with the bamboo radical over 壽, 筹 depicted small bamboo sticks used as counting tallies or chips in ancient China. From this concrete sense of 'counting rod' it extended to mean 'to count, plan, or scheme,' as seen in modern words like 筹划 (plan) and 筹码 (chip, bargaining counter).