name of one part in electrical cables
It is a cable "strain relief*. 

These are designed to prevent the cable bending sharply where it enters the appliance otherwise the cores are likely to fracture internally or the insulation crack.



Figure 1. A progressive strain relief

The progressive strain relief gets thicker and more resistant to flexing the closer it gets to the point of entry into the appliance. Even with a strong pull on the cable the radius of bending at the point of entry to the appliance can be kept reasonably large while the weak end pulls almost in line with the direction of the pull.

Note also that in your photo a hanger has been incorporated into the strain relief. This provides a means of hanging the tool securely other than hanging by the cable. The cable is typically not designed for carrying mechanical loads.

Edit: as pointed out in the comments below and clearly visible on close examination of the photo (when not bleary eyed), that's a chuck key holder. It does, however, make a good place to hang the drill!