Gaddi is the seat of a shop owner or merchant. The Rekhta dictionary also gives its wider meanings, power and the seat of authority. Gaddi par baithna, to sit on the gaddi, means to take the place of a senior or an elder, a pir or a guru.
Bada sahab, the big sahib, is the head of a department. Rekhta’s Urdu entry for bade sahib names the chief officer of a district, and also the senior member of a household.