The title of the 'Ambassador of Hindu-Muslim Unity' was given to Muhammad Ali Jinnah by Sarojini Naidu.

Background:
- Muhammad Ali Jinnah was a prominent leader of the Indian National Congress and played a significant role in the Indian independence movement.
- He initially advocated for Hindu-Muslim unity and cooperation in the struggle against British colonial rule.
- However, as the political landscape evolved and communal tensions increased, Jinnah began to advocate for the creation of a separate nation for Muslims, which eventually led to the formation of Pakistan.

Sarojini Naidu:
- Sarojini Naidu was a prominent freedom fighter, poet, and politician. She played an active role in the Indian independence movement.
- Naidu was a close associate of Mahatma Gandhi and was known for her eloquence and oratory skills.
- She had a deep understanding of the complexities of Indian society and was committed to promoting communal harmony and unity.

The Title 'Ambassador of Hindu-Muslim Unity':
- Sarojini Naidu, recognizing Jinnah's efforts towards Hindu-Muslim unity, bestowed upon him the title of the 'Ambassador of Hindu-Muslim Unity.'
- This title reflected the recognition of Jinnah's role in bridging the gap between the two communities and promoting harmony during a time of growing communal tensions.
- It also acknowledged his efforts in working towards a united and inclusive India.

Significance:
- The title of the 'Ambassador of Hindu-Muslim Unity' highlights the early phase of Jinnah's political career when he was still advocating for a united India.
- It showcases the recognition of Jinnah's efforts towards promoting communal harmony and his commitment to the idea of a united nation.
- However, as time passed, Jinnah's political stance shifted, and he eventually became the leader of the All India Muslim League, advocating for a separate nation for Muslims.
- The title serves as a reminder of the challenges and complexities of achieving unity in a diverse and multicultural society like India.

In conclusion, Sarojini Naidu, a prominent freedom fighter and politician, awarded Muhammad Ali Jinnah the title of the 'Ambassador of Hindu-Muslim Unity' in recognition of his efforts towards promoting communal harmony and unity during the early phase of his political career.