Step 1: About Baburnama.
The Baburnama is the autobiography of Zahir-ud-din Muhammad Babur, the founder of the Mughal Empire. It describes his life, conquests, geography, flora, fauna, and culture of the regions he encountered.
Step 2: Language of composition.
Baburnama was originally written in Chagatai Turkish, which was Babur’s mother tongue. Later, it was translated into Persian during the Mughal period because Persian was the court language of the empire.
Step 3: Conclusion.
Thus, the original language of Baburnama was Turkish.
\[
\boxed{\text{Turkish}}
\]