I know it's possible to create a group of fields for a SharePoint Form Library and turn the group into a repeating section, but it possible to create a repeating section for a SharePoint List Form?
From my research I found the way to make get repeating sections on SharePoint List is by checking the "Manage multiple list items with the form." Checkbox. I also discover if you do not check this option from the initial create of the SharePoint List you will NOT be able to check it later if you decide you want repeating sections.
The website I found most of my research is: InfopathDev Forums
To clarify the answer above, you can check off the "Manage multiple list items with the form" when you create a list from Infopath's side.
Add a Repeating Section. Inside this Repeating section, add another Repeating section. In the second repeating section, insert a Drop Down List Box. Right Click on the Drop Down List Box --> Properties --> Get choices from an external data source.