The word Dr. Seuss coined in *If I Ran the Zoo* was “nerd.” The 1950 book is often credited with the first documented printed appearance of the word in modern English, although Seuss used it simply as the name of an imaginary creature.
The word appears in a fantastical list of animals Gerald McGrew says he would bring back to his zoo: a Nerkle, a Nerd, and a Seersucker. The Nerd is not described as an intelligent or socially awkward person in the book; those meanings developed later.
By 1951, “nerd” was being reported as slang for an uncool or boring person. Over subsequent decades, the word acquired its familiar association with intense intellectual interests, technical knowledge, and social awkwardness.
A common mix-up is treating Seuss as the unquestioned inventor of the modern insult. His book provides the earliest famous printed example, but the word’s ultimate origin remains uncertain, and its modern meaning emerged after the book.