What do campsite, earwax, and doorknob have in common?

Eliana has been learning about compound words at school. At dinner tonight, she was explaining to us what a compound word was: two words that are put together to make one word. We asked for an example ... and she promptly told us, "Thanksgiving!" Impressed, we began a discussion of other compound words: backyard, butterfly, catfish, into, campsite, hairbrush, sweatshirt, basketball, volleyball, cheerleading, schoolhouse, icebox, doorknob, dishwasher, birthday, wallpaper, earwax, eyelid, lipstick, bookshelf .... and there were many, many more, most of which Eliana came up with on her own. 

As we're coming up with all these compound words (and plenty that aren't) Olivia was trying to help. She came up with lipstick (which was actually pretty impressive), and then she pipes up, "How about stay-in-your-boundaries?"