What is "shahrastani"

Shahrastani (1983–2011) was an American-bred, British-trained Thoroughbred racehorse. He won four of his seven races between September 1985 and October 1986. He is best known for his performances in the summer of 1986 when he defeated Dancing Brave in the Epsom Derby, and won the Irish Derby by eight lengths. At the end of the season he was retired to stud, where he made little impact as a stallion. He died in 2011.