Holden Caulfield is doing something that must be against the school rules and something his parents certainly wouldn't want him to be doing. He is going to spend a couple of days in Manhattan all by himself, though he is only sixteen years old. This is probably why he balks at giving Mrs. Morrow his real name.
"Rudolf Schmidt," I told her. I didn't feel like giving her my whole life history. Rudolf Schmidt was the name of the janitor of our dorm.
Mrs. Morrow asks Holden his name because she wants to tell her son Ernest she met him on the train. Ernest's mother is the talkative type. If she knew Holden's real name she would not only tell her son but she might tell others. For all Holden knows, she might even know his parents--or might know people who knew his parents. It would seem that the whole string of lies he tells her about her son is intended to keep her from asking him more questions about himself.
Holden is smart enough to know that if he told her his real name she might go on to quiz him about what he calls his "whole life history." I think we have all had the experience as children of getting involved in conversations with adults that turn into what feels like the third-degree. Holden has to answer a lot of personal questions when he talks to Mr. Spencer and again when he talks to Mr. Antolini. Adults seems to think they have a right to ask kids one question after another. "How old are you?" "Where do you go to school?" "What's your favorite subject?" "What do you major in?" "What do you plan to do when you graduate?" "What does your father do?" "What does your mother do?" "Do you have any brothers or sisters?" Give me a break!
Holden is going to an upper-class private school. A lot of the boys' parents probably know each other, either socially or in the business or professional worlds. Holden has gotten into these kinds of conversations before and senses that he might give away information he doesn't want to divulge. When the novel opens, Holden shows that he is sensitive about protecting his family. He says he doesn't want to go into "all that David Copperfield kind of crap."
In the first place, that stuff bores me, and in the second place, my parents would have about two hemorrhages apiece if I told anything pretty personal about them. They're quite touchy about anything like that, especially my father.
The novel doesn't tell us about what happened when Holden finally met up with his mother and father again--but chances are that they never found out he had spent all that time alone in Manhattan. Chances are that they never learned he took his little sister Phoebe out of her school to go riding on the merry-go-round. Phoebe is pretty good at lying, too. What grown-ups don't know can't hurt them.
Holden Caufield, the protagonist of J. D. Salinger's novel The Catcher in the Rye, meets Mrs. Morrow, the mother of Ernest Morrow, one of his classmates, on a train after he has flunked out of Pencey Prep. Mrs. Morrow is obviously very proud of her son, and pleasant to Holden.
Mrs. Morrow's son, Ernest, is actually unpopular and Holden dislikes him. Privately he thinks:
Her son was doubtless the biggest bastard that ever went to Pencey, in the whole crumby history of the school. He was always going down the corridor, after he'd had a shower, snapping his soggy old wet towel at people's asses.
Instead of saying this, he invents a story to the effect that Ernest could have been class president but was too shy to allow his name to be put forward.
Holden also, rather than admitting that he has flunked out of school, invents a story about a medical emergency. Out of a combination of shame at his lies and his wanting to preserve his privacy, he gives Mrs. Morrow the school janitor's name rather than his own.