Nobody actually knows how Fibonacci died. The exact date of his death, in fact, is still a mystery. It is estimated that he died sometime in the decade between 1240 and 1250. He lived to be approximately 70 to 80 years old.
Fibonacci was famous for transforming mathematics in Europe. Prior to writing his book "Liber Abaci," Roman numerals were used for calculations. Realizing that this was too confusing, Fibonacci used the Hindu-Arabic numeral system in his book which soon became the standard in Europe. Although he did not create the Hindu-Arabic numeral system, they were soon called Fibonacci numbers because he used them in his book.