Final answer:
The 'Chaali Mukte' were forty Sikhs who, after renouncing Guru Gobind Singh Ji, fought alongside him against the Mughals on December 29, 1705, earning the title of 'Chali Mukte' or the Forty Immortals and transforming Khidrana into Muktsar, the Pool of Liberation.
Step-by-step explanation:
The 'Chaali Mukte', referred to in the Sikh 'Ardas', were forty Sikhs who had initially renounced Guru Gobind Singh Ji but later realized their mistake and fought valiantly for him. This took place near the lake of Khidrana, also known as Isharsar, on December 29, 1705, where they got martyred fighting against the Mughals. Following their act of bravery and ultimate sacrifice, Guru Gobind Singh Ji bestowed upon them the title of 'Chali Mukte', translating to the Forty Immortals. After this incident, the site of Khidrana became known as Muktsar, which means the Pool of Liberation, commemorating the sacrifice of these forty individuals who upheld the values of Sikhism in face of religious persecution by the Mughal Empire.