I saw a legion called Santi. What does sandy mean?

The word "Three-body" comes from Mr. Liu's novel "Three-body". Alpha Centauri has a star system called triple galaxy, but it is different from the solar system because they have triple galaxies? Therefore, it is called trisomy.

Ps: The great destruction of three giant stars directly led to the inability of three-body stars to survive, so they migrated.

The bird's nest is the optimal solution, but the three-body has no solution.