Haidar or Haider [Devnagari:हैदर,Arabic:حيدر] is an Arabic word, which means lion.
It's a common Muslim name throughout the world, including India, where Haider Ali was a famous Indian de facto ruler, and father of Tipu Sultan, who ruled over the Kingdom of Mysore.
Haider is also the name of Vishal Bhardwaj's film based on Hamlet. Vishal has earlier made Maqbool and Omkara, based on Shakespearean plays Macbeth and Othello. As you may notice, the names of movies (and the characters) have the same first letters, a practice he has been following since Maqbool, for all the important characters of movies.