How do I remove the app attribute in my order details?

All products added to the shopping cart using the 'Add to Cart' button in that app and when purchased, include the Shopify cart attribute '__Added with Also Bought button'.

This attribute can be used for app auditing and will appear on your Shopify order details page:

The double underscore prefix is a Shopify convention that instructs your Shopify theme and other third-party apps that it should not be displayed to your customers.

Anyway, if you prefer to not have that auditing attribute, you can easily disable it from the app preferences page, inside 'Tracking preferences':