Fun fact: every single male Sikh in the world has the last name Singh. That's not a joke. The tenth and final human Guru, Gobind Das, declared that all male Sikhs would take this name, which means lion and connotes high birth (he became Gobind Singh). Likewise, all female Sikhs have the surname Kaur. Why? Well, knowing one's family name means you can figure out that person's caste, so eschewing family names for uniform surnames was an act of rebellion against the caste system and an attempt to reduce caste-based prejudice.