The dynasty was founded in 909 by Ë AbdullÄ h al-Mahd Ä `` Billah , who legitimised his claim through descent from Muhammad by way of his daughter FÄ tima as-Zahra and her husband Ë AlÄ `` ibn-Ab Ä `` - TÄ lib , the first ShÄ `` Ë a ImÄ m , hence the name al-F Ä timiyyÅ `` n `` Fatimid '' . Ubayd Allah made his claim through his descent from Muhammad by way of his daughter FÄ tima as-Zahra and her husband Ê '' AlÄ `` ibn-Ab Ä `` - TÄ lib , the first ShÄ `` Ê '' a ImÄ m , hence the name al-F Ä timiyyÅ `` n `` Fatimid '' .