How to set a custom name for a backend grid's column?

You can do it by specifing a class for the column:

An example of class declaration:

The class should implement the \Magento\Ui\Component\Listing\Columns\ColumnInterface

The \Magento\Ui\Component\Listing\Columns\ColumnInterface inherits from the \Magento\Framework\View\Element\UiComponentInterface, which has the getName() method:

By default the \Magento\Ui\Component\Listing\Columns\ColumnInterface is implemented by the ancestors of the \Magento\Ui\Component\Listing\Columns\Column class

It has the following getName() method implementation:

So it just returns a value of the name attribute, for example:

If you create a custom getName() method implementation, you will get a custom name for a backend grid column.