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Beloved children’s book author Dr. Seuss would have turned 108 today, and he would surely have been proud to see that his works are still relevant as ever, resonating with children—and adults—of all ages. Born Theodor Seuss Geisel in 1904, the writer produced more than 60 children’s books before his death in 1991.

So many of his books are classics, marking milestones of their readers. Both the book and the film adaptation of How the Grinch Stole Christmas are holiday classics. Oh, the Places You’ll Go is a wildly popular high school and college graduation gift. And one in four American children receives a Seuss work as his or her first book.

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While many of us know him through the lens of his beloved characters, there was much more to Geisel than his drawings and rhymes. Below are a few things you may not have known about good ol’ Dr. Seuss:

Geisel started using the pen name Dr. Seuss after he was forced to resign from his post as editor-in-chief of the Dartmouth humor magazine, Jack-O-Lantern. He was caught throwing a party and drinking gin with his friends in his room, and because this was back during Prohibition, he had to pay the price. He managed to keep writing for the magazine, but under the pseudonym “Seuss,” which was his mother’s maiden name. He started using “Dr. Seuss” after he graduated college, as a consolation to his father for never pursuing medicine.

The Cat in the Hat author originally said the correct pronunciation of “Seuss” rhymes with “voice.” He later changed it to rhyme with “goose,” as it was how most people pronounced it.

Geisel also wrote under the pen names Theo LeSieg and Rosetta Stone.

He is said to have coined the word “nerd.” According to TheFW.com, the first recorded instance of the word “nerd” is in Seuss’ 1950 book, If I Ran the Zoo.

Before he started writing children’s books, Geisel was an ad man, creating satirical advertisements for General Electric, Standard Oil, NBC, and others. He was also a World War II political cartoonist, and joined the Army as a Captain, making educational and propaganda films. Two documentary films based on works he created (Hitler Lives? and Design for Death) won Academy Awards.

Dr. Seuss practiced what he preached: his first book, And to Think I Saw It on Mulberry Street, was rejected by 27 different publishers before it finally got picked up. “Think left and think right and think low and think high. Oh, the thinks you can think up if only you try!” Seuss once wrote. Try, try, try again, he did.

Though he knows how to write for children and their wild imaginations, he never had kids of his own. “You make ’em, I amuse ‘em,” he once said. His wife said in an interview once that he “couldn’t just sit down on the floor and play with them,” and was always a bit uncomfortable and afraid around them.

He had a bit of a dirty mouth, and would try to sneak in some PG-13 language into his works. The first version of “Hop on Pop” that was sent to his publisher included the word “contraceptive” in one of the verses.

Geisel considered his greatest achievement to be killing off the Dick and Jane books, which he said weren’t challenging enough for children, and were boring. Dr. Seuss’ books became the new standard in children’s publishing—expanding the imagination through brilliant illustration, social issues, and clever rhymes and vocabulary.

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