This term in the needlework world has nothing to do with aliens, it simply means unfinished objects. It seems that many crafters love to start projects but have a hard time getting them finished. They languish on shelves, in drawers, or put completely out of sight in boxes. You can tell I am speaking from experience here.
Meanwhile, we just found this UFO belonging to my deceased mother-in-law.
Hubby discovered this partly needleworked Siamese cat in an old suitcase. And it comes complete with all the wool which appears to be in immaculate condition. Just begging to be finished.
So it is true you can inherit UFO's too. And just like your debts you can also outlive them. So who will inherit yours? :)