how did it get the name?
: American Pharoah's name is inspired by that of his sire, the Nile, and his dam's sire, Yankee Gentleman. The horse's name also acknowledges his owner Amhed Zayat's own Egyptian-American background.
American Pharoah
American Pharoah's name is inspired by that of his sire, the Nile, and his dam's sire, Yankee Gentleman. The horse's name also acknowledges Zayat's own Egyptian-American background. 
who won the triple crown before american pharaoh Affirmed.
wiki:20003674
American Pharoah [SEP] Name
American Pharoah's name is inspired by that of his sire, the Nile, and his dam's sire, Yankee Gentleman. The horse's name also acknowledges Zayat's own Egyptian-American background. The misspelling of "Pharaoh" is permanent, but inadvertent. Zayat originally claimed that the spelling was the result of an error by The Jockey Club, but the organization's president stated, "The name request for the 2012 colt American Pharoah was submitted electronically on January 25, 2014, through The Jockey Club's interactive registration site. Since the name met all of the criteria for naming and was available, it was granted exactly as it was spelled on the digital name application." Zayat later retracted his statement.