You can edit Lesson Items' names after they have been created.
Once you have a Course selected in the Courses and Groups dropdown menu, click the Lessons link in the Course Navigation bar.
Hover over the bar of the Lesson Item and click the Edit link.
Edit Item Details
You can edit the Item title by typing in the title field.
Once you are done making changes, click the Save button.
Note: Changes made to one item will be made to all iterations of the item.