This is the 7415th most frequent Japanese word.
余す
"余す" means "to leave over" or "to save something for later."
Here, '余す' is used to indicate that some work is left or remaining.
このプロジェクトは難かしく、まだ多くの作業を余している。
This project is difficult and still has a lot of work remaining.
In this sentence, '余す' is used to express 'not leaving anything out', highlighting completeness.
私たちはその美しい景色を余すところなく楽しんだ。
We fully enjoyed the beautiful scenery.
The usage of '余す' here conveys the idea of thoroughness, without leaving any part unspoken.