Sentence:  "Good,—that's a whack. What's your name?" / "Becky Thatcher. What's yours? Oh, I know. It's Thomas Sawyer." / "That's the name they lick me by. I'm <WSD>Tom</WSD> when I'm good. You call me <WSD>Tom</WSD>, will you?" 
Meaning of the word marked with <WSD> tags:  (diminutive=Thomas), also used as a formal male given name.