I have fallen HARD into all things mermaid, I would love to know more about Wave! Absolutely anything you’d like to share.😁
He had to do speech therapy after his first quest.
When fighting Ganondorf, he was severely injured on the neck, damaging his vocal cords, and was going to die but Zelda saved him using healing magic and blessings from Hylia. So, he is selective mute due to medical conditions (not the full backstory*).
In speech therapy (I know from experience), a common word they use is "Apple" to try and help people pronounce different letters. So, Wave/Courage had to use it.
If you can't pronounce things properly, they might sound like other words.
"Apple," when pronounced wrong, can sound like "Asshole."
He said "Asshole" instead of "Apple."
When he can speak—without a large amount of pain—he likes to say the "Apple" over and over again (typically done when he is overwhelmed).