In the DC comics, Mr. Terrific is Michael Holt’s superhero name, and he’s actually the second hero to adopt that moniker. The original Mr. Terrific, Terry Sloane, was a gifted, brilliant man who had been born with many advantages and was upset that others didn’t have the same chances and benefits that he did. Hence, he fought for justice to make the world a fairer place, and made his motto “fair play.”
Holt adopted the motto along with the identity, and put the phrase along the sleeves of his badass jacket. The other main aspect of his costume is a giant “T” on his face, which stands for, you guessed it, “Terrific.” None of this is exactly subtle, but it’s great.
In the Arrowverse, Terry Sloane wasn’t a crime fighter, but a pro wrestler. Curtis admired the man but his motto was still “fair play.” He was so good that he didn’t need to cheat to win. Even though the other Team Arrow recruits kind of made fun of his jacket, Curtis stood by his hero as he set out to become one of his own — with a snazzy new mask to boot.