When the CFL was formed, they were allowed to keep their long-standing names; Ottawa was frequently known as the "Eastern Riders" while Saskatchewan was referred to as either the "Western Riders" or "Green Riders".
(From Wikipedia)
After soliciting suggestions for a new team name in November, the green-and-gold-clad team eventually winnowed the options down to seven, all beginning with the letter “E.” In February, those choices were reported to be Eagles, Eclipse, Elements, Elk, Elkhounds, Evergreens and Evergold. (Jun. 1, 2021)