The term round-robin is derived from the French term ruban, meaning "ribbon". Over a long period of time, the term was corrupted and idiomized to robin.
In a single round-robin schedule, each participant plays every other participant once. If each participant plays all others twice, this is frequently called a double round-robin.
Below is a simple example of Round Robin Tournament Schedule generated using https://eventbracket.com an online tournament and bracket management application online.