I have no idea what chapter but the question I am asking says "why does Herbert use the nick-name "Handel" for Pip?
This happens as Herbert and Pip are getting to know each other. Herbert recognizes Pip growing into his great expectations and wants to help Pip.
One of the ways he wants to help is by giving Pip an identity that feels grown up. Pip is not a name for a grown man, and Pip's Christian name, Philip, is
like a moral boy out of the spelling-book who was so lazy that he fell into a pond, or so fat that he couldn't see out of his eyes...
Quite frankly, Herbert didn't like Pip's name and renamed him.
The information you are looking for is in Chapter 22 of the book. The quick answer is that Herbert calls Pip that as a compliment."
As you may know, Handel was the last name of a famous composer of music. Herbert really liked a piece of music that Handel had written called "The Harmonious Blacksmith. So he also calls Pip Handel because he thinks he and Pip get along well and because Pip was once a blacksmith.
I think Herbert calls him this also as a token of respect -- calling him by the name of an important person.