A term widely adopted by British regular soldiers serving in India or having contact with Indian troops.
Etymology
From Hindiबन्दूक(bandūk, “gun”), from Arabicبُنْدُقِيَّة(bunduqiyya, “rifle, gun”). The original Arabic was بُنْدُق(bunduq) and denoted filberts, nuts shaped like the projectiles thrown from stone bows. That usage was eventually transferred to the bows themselves and eventually to firearms.