What is "at-turtushi"

'Abu Bakr Muhammad at-Turtushi (1059 – 1126 CE) (451 AH – 520 AH ), better known as At-Turtushi was one of the most prominent Andalussian political philosophers of the twelfth century. His book Kitāb Sirāj al-Mulūk (The Lamp of Kings) was one of the most important works of political theory to be produced in the medieval Islamic world. At-Turtushi was also an accomplished jurist in the Maliki school.