The mermaid line, also known as the mermaid line, is officially called the "external oblique muscle", which means that the two lines on both sides of the male abdomen near the upper pelvis form a V-shape, so it is called the mermaid line because it is similar to the slightly contracted shape of the lower part of the fish. Leonardo da Vinci first proposed "mermaid line" as an indicator of "beauty" and "sexiness" in "On Painting".
Recently, however, with people's pursuit of mermaid line, many healthy women who love beauty have also exposed their own mermaid line, claiming that mermaid line is not a unique physiological phenomenon for men.