What does the "iron hand" in photography mean?

Generally, when shooting with a handheld camera, if the shutter speed is too slow, the photos taken will be blurred due to hand shaking.

Like ordinary people, when shooting with a 28mm lens, if the shutter speed is lower than 1/30S, the possibility of blurring is very high.

Those so-called Iron Hand masters are said to be able to hold 1/10S or 1/4S or even 1S, and the photos they take are not blurry. They are definitely masters who have practiced the "Iron Hand Skill" ah!