last updated 7 Aug 2019
Khan is the most common surname in Pakistan, Afghanistan and Saudi Arabia.

Genghis Khan (1162-1227) was the founder and first Great Khan of the Mongol Empire, which became the largest contiguous empire in history after his death.

Khan has many equivalent meanings such as "commander", "leader", or "ruler" "king" "chief". As of 2015 khans exist in South Asia, Central Asia, Eastern Europe and Turkey.

It came to the Indian subcontinent by way of Timur and the Timurid dynasty, who were Islamic - the surname Khan as a result has associations with Islamic ethnic identity in Pakistan and India (it's not a label, though - there are Sikh, Hindu and Christian folks with the surname Khan as well.)

Following from (13) Is Khan a Muslim name? - Quora

Kahn (Mongolian: хан/khan; Turkish: kağan or hakan; Azerbaijani: xan; Ottoman: han; Old Turkic: \U00010c34\U00010c0d\U00010c23, kaɣan; Chinese: 可汗, kèhán; Goguryeo : 皆, key; Silla: 干, kan; Baekje: 瑕, ke;Manchu: ᡥᠠᠨ, Pashto: خان Urdu: خان‎, Balochi: خان Hindi: ख़ान; Nepali: खाँ Bengali: খ়ান; Bulgarian: хан,

Pashto: امان خان
Manchu: ᠬᠠᠭᠠᠨ

The Manchu alphabet is written left to right in vertical columns running from top to bottom.