According to John Everett-Heath, the author of Oxford Concise Dictionary of World Place Names, Hyderabad means "Haydar's city" or "lion city", from haydar (lion) and ābād (city). It was named to honour the Caliph Ali Ibn Abi Talib, who was also known as Haydar because of his lion-like valour in battles. Andrew Petersen, a scholar of Islamic architecture, says the city was originally called Baghnagar (city of gardens). One popular theory suggests that Muhammad Quli Qutb Shah, the founder of the city, named it "Bhagyanagar" or "Bhāgnagar" after Bhagmati, a local nautch (dancing) girl with whom he had fallen in love. She converted to Islam and adopted the title Hyder Mahal. The city was renamed Hyderabad in her honour. According to another source, the city was named after Haidar, the son of Quli Qutb Shah.