Dick Grayson made his own language when he was young.
While at Haley's Circus, he and a few other circus kids decided they needed a way to communicate without the adults knowing what they were saying. That’s when Dick came up with his language. It was originally nonsensical, but later took on structure and syntax.
Between practices, Dick would write the rules and words into a dictionary. Fast-forward a few years, and you are helping Dick clean out a few things from his old room in the manor. That's when you find it, the dictionary.
Dick's ears burned as you showed him the book. He tried to pry the book away from you, but you weren't having it. You read out a couple of words, poorly.
And Dick couldn't help but correct you, through mortified murmurs. You'd say the word slowly this time, stumbling again. Dick corrects you one more time, exaggerating the pronunciation.
Then you get it and beam at Dick, sapping all his need for air. You ask Dick to teach you a few more words.