Muslim (found almost exclusively among Sunni Muslims): from an Arabic personal name of uncertain etymology. It is thought to be related to Arabic ῾āmir, which means ‘prosperous’, ‘full of life’, ‘large’, ‘substantial’. The root word ῾umr means ‘life’. ῾Umar bin al-Khaṭṭb was the second of the ‘rightly guided’ khalifs (ruled 634–44). He was known by the title al-Fārūq ‘the distinguisher’, i.e. one who distinguishes between truth and falsehood. He was one of the Companions of the Prophet Muhammad. The Persian poet ῾Umar al-Khayyām (1048–1125), also known in English as Omar Khayyam, is the author of the classic poem, the Rubaiyyat.