The person who has been known as the `Frontier Gandhi` is Khan Abdul Ghaffar Khan. He was a prominent leader in the Indian independence movement and a close associate of Mahatma Gandhi. Khan Abdul Ghaffar Khan, also known as Bacha Khan, was a Pashtun political and spiritual leader who believed in non-violent resistance against British rule in India. He was a champion of the rights of the Pashtun people and worked tirelessly for their social and political upliftment. His commitment to non-violence and his efforts to promote peace and unity among different communities earned him the title of `Frontier Gandhi`. It is important to note that none of the other options listed - Khan Saheb, Chaudhary Shaukatullah, and Liaquat Ali Khan - are known as the `Frontier Gandhi`.