Pumpkin = pumpkin patch, pumpkin pie
Cupcake = cake cup
Snow = snowflake, snowball
Airport = airplaneport, but
Airplane = hairplane [my wife reminded me of these two]
After I'd been working in France a while, a French colleague asked me if I realized that some word or grammatical construct I used all the time actually meant something completely different than how I was using it. When I asked why he hadn't told me this sooner, he laughed and said, "Because you always use it so confidently. And anyway, it's always amusing."
I remembered this as I was thinkgng of the words K2 has emphatically, excitedly, and consistently wrong, and yet we don't really try too hard to correct her.