Black hole is simply called so because it traps Light that enters it. Once it enters, even Light cannot escape out. This is because of their gravity created because of dense mass packed in small space. Black holes are thought to be created by collapsing giant stars. They are potentially capable of swallowing the universe.
It represents the Inconscient that holds Light within itself and offers utmost resistance for its release.
Affectionately,
Alok Da