Before removing Origami, make sure that you closed all the copies of Adobe Illustrator. If you leave one, a plugin installed there will not be removed.
On Windows, you simply uninstall Origami like any other application, it will remove all the installed extensions automatically.
On Mac, you need to run Origami first and click the “Illustrator” menu, then “Uninstall Extensions”. This will remove all the extensions, then you need to quit Origami and remove it by dragging it into the Trash bin.
Visit here if you need more detailed instructions on removing the application.