Anticipation is, in short, the wind-up action before a larger action. As a basic example, in order to jump one must squat down first then shoot up. This idea is supported by the arc principle of animation. Let’s say you’re throwing a punch, to be able to put your weight behind it, you need to pull back and then lean into it, ultimately creating an arc. It is then further supported with the idea of secondary actions where a person’s body rotate slowly in the opposite direction. Basic path is anticipation>arcs>secondary action>follow through.  

https://learn.toonboom.com/modules/animation-principles/topic/anticipation-principle

https://pixune.com/blog/anticipation/