A recent tweet from CursorTN does a nice bit of frame semantic analysis: the expression for being irrationally in love *should* be "heels over head in love." Think about it.
Hmmmm, yes, yes, this seems correct. What the hell does 'head over heels' mean anyway? I'm head over heels right now and I'm sitting at a computer typing!
Presumably there is a romantic attraction frame (can't find anything like this at FrameNet, might have missed it) whereby being in love upsets your natural state. if your natural physical state is standing upright, then you naturally are 'head over heels.' Hence, when you are in love, your natural state is up ended and you become 'heels of head.' And yet this is not the phrase in use.
A little googling and I found a few websites which have discussed this before, but only one gives us some historical background:
The Phrase Finder: 'Head over heels' is a good example of how language can communicate meaning even when it makes no literal sense. After all, our head is normally over our heels. The phrase originated in the 14th century as 'heels over head', meaning doing a cartwheel or somersault.
Now can we figure out how the reversal occurred?