In chapter 4 of Andrew Clements's Frindle, Nick begins his research for his report on how words get added to the dictionary by reviewing an article titled "Words and Their Origins," found at the front of his new dictionary, which he purchased at Mrs. Granger's recommendation. The opening sentence of the article is definitely very long and complicated, full of words that are a bit beyond Nick's fifth-grade-level vocabulary, even though he is a very avid reader in his spare time. Since the words in the sentence and its sentence structure are so complex, Nick compares reading the sentence to reading the "ingredients on a shampoo bottle," which means he thinks reading the sentence is very difficult (21).
Ingredient lists found on personal care products, like shampoo bottles, are full of the names of chemicals and organic compounds used to make the products. If these names are unfamiliar to a reader, then reading a list of ingredients will feel similarly to reading a foreign language. This is how Nick felt when reading the sentence he found in the dictionary. Phrases such as "embodies unparalleled etymological detail" and "superb lexicographic scholarship" would have been completely foreign to Nick, making it difficult for him to understand what the sentence is saying.
In chapter four of Frindle, Nick starts reading the new red dictionary that his mom has purchased because his teacher Mrs. Granger insisted that he would need it. Nick has been assigned words to look up in the dictionary—a time-consuming task for the fifth grader—and he must write a report on where words come from.
To fulfill the latter task, Nick begins reading the introduction to the dictionary, entitled "Words and the Origins." Because this essay is complex, boring, and contains a vocabulary that is higher than his reading level, he feels like this task is "like trying to read the ingredients on a shampoo bottle." Ultimately, it seems like a bunch of nonsense to him.
However, it is this exploration of the dictionary that ultimately gives Nick the inspiration to make up a word of his own—the so-called "frindle," or "pen," of the book's title.