Conversation so far:
who is oscar the grouch's best friend
For several seasons, Oscar the Grouch was frequently shown with his friend and pet Slimey, an orange worm.
Does Oscar the Grouch have any other friends besides Slimey?
The only person Oscar the Grouch has ever liked on-camera was Maria, which he would never admit.
What's Oscar the Grouch's personality like?
Oscar the Grouch openly admits that he does not like anything or anybody that is nice, except young human children.

Question: Is that why the character is called the Grouch?
Self-contained rewrite: Is not liking anyone who is nice the reason why Oscar is called the Grouch?