The word Gadh in north Indian languages like Hindi, Gujarati, Rajasthani, Marwari, Marathi means a fort, like Chittorgarh, Sinhgadh, Mehrangadh.
The persons who were expert and had skilled knowledge to plan and build a fort were called Gaidher or Gajdhar.
The kings used to trust them and they had the power and authority to hire manual laborers and skilled masons for such construction works.
In Madhya Pradesh, Gajdhar was a title awarded to the city architects and held an important place in the royal court and were looked upon with respect.
In India or persons of Indian origin you can find many people using Gaidhar or Gajdhar as a surname.