This word is taken from the translation of western literature, "Deep water flows slowly, shallow water surges violently", and it is also translated as "shallow water is noisy, deep water is silent", which is a famous saying of the poet Shelley.

In other words, the depth is not necessarily reflected in the appearance, but the water is shallow. Deep water is silent because it has too much load and a broad mind, and can accommodate all rivers. Maybe this is the realm of silence.

Superficial or profound, we can't just rely on external things like bluffing, but the connotation is more important.

Together, this should be an abbreviation.