The Blue Wizards are The Lord of the Rings’ most mysterious Istari. The Istari are a huge presence in The Lord of the Rings, even though many don’t realize it. Gandalf is the most famous Istar, followed by Saruman, followed by Radagast. Istar means “Wizard” in the Elvish language of Quenya, hence why this esoteric group of characters is so named. The Istari are mentioned in J.R.R. Tolkien’s The Lord of the Rings, but Peter Jackson’s famous trilogy adaptation tends to just use the term “Wizard.” The Silmarillion and Unfinished Tales explain the Istari further.

https://screenrant.com/lord-of-the-rings-blue-wizards-istari-explained/