The model name stands for broad gauge (W), Diesel (D), Shunting (S) engine, 6th generation (6).

This class was designed in 1975 to address the need for a powerful shunting locomotive with the ability to haul 20- to 24-coach rakes.

The previous WDS-4 class was found to be grossly underpowered for this kind of operation.

A WDS-6 locomotive basically consists of a YDM-4 powerpack (a 6-cylinder, 4-stroke, inline, turbo-supercharged ALCo engine) mounted on a WDM-2 body frame.

Beginning in 1975, these were initially manufactured solely by BLW, Varanasi, but later, the Parel Workshop started building them using CKD (completely-knocked-down) kits provided by DLW.