Head Over Heels

I was thinking about the phrase "head over heels". I've seen "Must Love Dogs" several times — it's the kind of movie I like to watch while sewing. When Bob/Bobby introduces himself to Sarah, she talks about her first boyfriend, who was named Bobby, and makes this cute little flip of her hands to indicate she was "head over heels" for him.

But isn't one's head always over one's heels? Wouldn't "heels over head" be more appropriate?

Why did I start thinking about this in the shower the other morning? Because I'm determined not to be head over heels for any man again anytime soon. The last time hurt too much when I hit ground. Well, hurt or made me feel like a fool.