This phrase can mean to turn over completely in a forward motion, as in a somersault. Or it can mean to fall madly in love. Since this is Valentine’s Day, we’ll take it to mean ‘head over heels in love.’
When it was first used, however, it only had one meaning: being temporarily the wrong way up. There are many similar phrases used to describe things that are not in their usual state: upside-down, topsy-turvy, ass over tea-kettle, bass-ackwards, and so on.
The first known written example of ‘head over heels’ is from Herbert Lawrence’s Contemplative Man, 1771:
“He gave [him] such a violent involuntary kick in the Face, as drove him Head over Heels.”
The first use of the phrase for falling in love comes from America in June 1833. The following example is from the Indiana newspaper The Lebanon Patriot, and the lack of quotation marks around the words or any explanation of them suggests that the expression was in common usage by that time.
“About ten years ago Lotta fell head over heels in love with a young Philadelphian of excellent family.”
‘Head over heels’ is a good example of how language can communicate meaning even when it makes no literal sense. Check your mirror: your head is normally over your heels. The phrase actually originated as ‘heels over head,’ meaning to do a cartwheel.
I don’t know why the words became reversed. Though I find that ‘head over heels’ rolls off the tongue more smoothly than ‘heels over head.’ Or do I merely think so because I’m so used to hearing it as ‘head over heels’?