Blueberry buckle

Blueberry buckle is basically a coffee cake made with blueberries and a streusel topping.  I've heard it described as so good it could make a bulldog climb a marble wall.
I made one this afternoon and darling husband wanted to know why it was called "buckle."  I said I didn't know--maybe because it was so good it would make your knees buckle.  He wasn't buying that, so I said maybe you would eat too much and have to loosen your belt buckle.  And while I was at my brilliant brainstorming, I said maybe it's from a German word.  (The recipe I used was supposedly from someone's grandmother in Pennsylvania...  Pennsylvania... Pennsylvania Dutch...  which is really German; okay that's how my mind works.)  The internet tells me it is because the topping has a buckled appearance.  I thought my etymologies were a little more interesting.