Cognomen 思吉 (Siji 
, 思吉 ) , in the world, is quite a rare family name. The family name 思吉 is characteristic of Western Asia, particularly Qatar, where it is quite a rare surname, United Arab Emirates, and Oman, where it is a rare surname. Measured by absolute frequency, it is the most numerous in India, Nigeria, and Indonesia. More prevalently, 思吉 is the forename as well as the last name.