Rhys is a variant of Reese. Reese originates in Welsh language and means "fervor, enthusiasm". Rhys can be both masculine and feminine, but is rather used as masculine. Reese, on the other hand, is more popular for girls in the U.S. It functions as a surname as well. Reese was popularized by its bearer, American actress Reese Witherspoon, and also by Reese's Peanut Butter Cups, named after its founder H. B. Reese.