What is Yojijukugo?
A yojijukugo is a Japanese expression comprised of 4 Kanji characters. Many yojijukugo are non-idiomatic but when used, the term “Yojijukugo” often refers to the ones that are idomatic. Many of the idiomatic yojijukugo have their origin from Chinese literature or from Buddhist teachings, while others are purely Japanese in origin.
An example of a non-idiomatic yojijukugo is 健康診断(Kenko-shindan). You can see that the word is comprised of four Kanji characters so it can be classified as yojijukugo. In the phrase, “Kenko Shindan”, 健康(Kenko) means “health” while 診断(Shindan) means “diagnosis”. When used together as in 健康診断(Kenko Shindan), it means “medical examination”.
Another example of a non-idiomatic yojijukugo is the expression, 四字熟語(yojijukugo) itself. 四字(Yoji) is comprised of the Kanji characters, 四 and 字 which have the meaning of “four” and “letter” respectively, while 熟語 is a word which has the meaning of “Kanji compound” or “phrase”. These words combine to create the term, 四字熟語(yojijukugo).
An example of an idiomatic yojijukugo is 四面楚歌(Shimen-soka). This yojijukugo derives from an excerpt from the Shiji, a Chinese text covering the history of ancient China. In the excerpt, general Xiang Yu of the Chu is surrounded by a Han army and hears songs of the Chu being sung from the direction of the Han army. From this, Xiang Yu thinks that even his troops have surrendered to the Han and despairs.
In the yojijukugo, 四面楚歌(Shimen-soka), 四面(Shimen) means “all sides/directions” while 楚歌(Soka) means “song of the Chu”. Thus, Shimen-soka is used to describe a situation in which one has no allies and is surrounded by enemies.
Tokyoblaze’s List of Yojijukugo