Wait, so… does -copter come *from* helicopter?
Yep! This is called rebracketing. Another famous example would be “-burger”: the original food item is named after the German city, [Hamburg]+[er], but got semantically reinterpreted as [ham]+[burger]. Now it’s used as a suffix indicating a type of sandwich.
Tell me this is some kind of joke
Also, painstaking isn’t a combination of pain-staking, but actually pains-taking