What is "sajaseong-eo"

In Korean, sajaseong-eo are four-character idioms, the analog of Chinese chengyu and Japanese yojijukugo, and generally but not always of Chinese origin. They have analogous categorization to the analogs in other languages, such as gosaseong-eo for historical idioms.

A list (in Korean) can be found at 부록:사자성어; a list with English translations may be found at: "Structure of four character idioms".