Rename Tabs and Labels in Salesforce Setup can be used to rename related list. Check the following steps for reference.

1. If the child object is a custom object: From Setup, go to Create > Objects > (Name of Object).

If the child object is a standard object: From Setup, go to Customize > (Name of Object) > fields.

2. Locate the custom lookup or master-detail field referencing the parent object.

3. Click the “Edit” link next to the relationship field.

4. Rename the “Related List Label”.

5. Remember to “Save” when finished.