Sardarji is a respectful term for a Sikh. "Sardar" is a Sanskritic word meaning "chieftan" or "leader" while adding "ji" shows respect, much like calling someone "Sir" in English. In premodern India, "sardar" was a catchall term for a soldier. When the Sikhs arose in the early modern period, they became known as sardars because they were originally a militant sect and most Sikh males were professional soldiers. Today the Sikhs still maintain this martial tradition, at least symbolically--every Sikh male carries a sword called a kirpan on his person at all times.