His name means tent maker. His most renowned book as a mathematician is "Treatise on Demonstration of the Problems of Algebra". He is supposed to have calculated the length of a year as 365.24219858156 days. He was made famous by Edward Fitzgerald in 1859 in a different field.
That was Omar Khayyam, the Persian mathematician, poet, astronomer, and philosopher, of course. Outside of Iran, thanks to Edward Fitzgerald, he's mostly famous for his Rubaiyat. Rubaiyat derives from Rubaiyaas, which derives from the Arabic word for the number 4, meaning a verse with four lines, or a quatrain. The Rubaiyat is a collection of Khayyam's quatrains -- he wrote 1000s of them. One of the more famous ones (Edward Fitzgerald's translation) --
The Moving Finger writes: and, having writ,
Moves on: nor all thy Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all thy Tears wash out a Word of it.
Even though Winston Churchill and Martin Luther King, Jr. have quoted the above quatrain in their speeches (MLK, in his speech Why I oppose the war in Vietnam says, "It is time for all people of conscience to call upon America to come back home. Come home America. Omar Khayyám is right 'The moving finger writes and having writ, moves on.'"), probably Omar Khayyam's biggest contributions are in the fields of mathematics and astronomy. He wrote the Treatise on Demonstration of Problems of Algebra. Importantly he generalized the algorithm for solving cubic equations (and some higher power equations). In his book, Omar Khayyam has this to say --
From the Indians one has methods for obtaining square and cube roots, methods which are based on knowledge of individual cases, namely the knowledge of the squares of the nine digits 12, 22, 32 (etc.) and their respective products, i.e. 2 × 3 etc. We have written a treatise on the proof of the validity of those methods and that they satisfy the conditions. In addition we have increased their types, namely in the form of the determination of the fourth, fifth, sixth roots up to any desired degree. No one preceded us in this and those proofs are purely arithmetic, founded on the arithmetic of The Elements (of Euclid).
On the lighter side, an extremely hilarious and interesting take on the theatrical managers of 1920s in Broadway by Wodehouse (from Little Warrior urf Jill the Reckless).
Mr.Goble is a theatrical Manager on Broadway and is putting on a musical comedy written and financed by Mr. Pilkington from England. Wally is an established writer and composer. Mr.Goble has just come to the sets during practice and has cut out a line about a watermelon from the hero's script.
The gentleman who was playing the part of Lord Finchley, an English character actor who specialized in London "nuts," raised his eyebrows, annoyed. Like Mr Pilkington, he had never before come into contact with Mr Goble as stage-director, and, accustomed to the suaver methods of his native land, he was finding the experience trying. He had not yet recovered from the agony of having that water-melon line cut out of his part. It was the only good line, he considered, that he had. Any line that is cut out of an actor's part is always the only good line he has.
"The speech about Omar Khayyam?" he enquired with suppressed irritation.
"I thought that was the way you said it. All wrong! It's Omar of Khayyam."
"I think you will find that Omar Khayyam is the--ah--generally accepted version of the poet's name," said the portrayer of Lord Finchley, adding beneath his breath. "You silly ass!"
"You say Omar of Khayyam," bellowed Mr Goble. "Who's running this show, anyway?"
"Just as you please."
Mr Goble turned to Wally.
"These actors . . ." he began, when Mr Pilkington appeared again at his elbow.
"Mr Goble! Mr Goble!"
"What is it now?"
"Omar Khayyam was a Persian poet. His name was Khayyam."
"That wasn't the way I heard it," said Mr Goble doggedly. "Did you?" he enquired of Wally. "I thought he was born at Khayyam."
"You're probably quite right," said Wally, "but, if so, everybody else has been wrong for a good many years. It's usually supposed that the gentleman's name was Omar Khayyam. Khayyam, Omar J. Born 1050 A.D., educated privately and at Bagdad University. Represented Persia in the Olympic Games of 1072, winning the sitting high-jump and the egg-and-spoon race. The Khayyams were quite a well-known family in Bagdad, and there was a lot of talk when Omar, who was Mrs Khayyam's pet son, took to drink and started writing poetry. They had had it all fixed for him to go into his father's date business."
Mr Goble was impressed. He had a respect for Wally's opinion, for Wally had written "Follow the Girl" and look what a knock-out that had been. He stopped the rehearsal again.
"Go back to that Khayyam speech!" he said, interrupting Lord Finchley in mid-sentence.
The actor whispered a hearty English oath beneath his breath. He had been up late last night, and, in spite of the fair weather, he was feeling a trifle on edge.
"'In the words of Omar of Khayyam' . . ."
Mr Goble clapped his hands.
"Cut that 'of,'" he said. "The show's too long, anyway."
And, having handled a delicate matter in masterly fashion, he leaned back in his chair and chewed the end off another cigar.