Originally posted by: Lady Black
I did not even notice that it was the same spell!
After I read the sixth book, I thought that the Levicorpus spell was only known by a few people but the fourth book contradicts that. In the fourth book, after the quidditch world cup, when the ministry officials are getting the muggles down from being stuck in the air,(thanks to the death eaters and they nasty ideas of fun)the ministry officials us the spell "Liberacorus" which counteracts "Levicorpus". If the ministry knew about it, then the spell must not have been all that unpopular.
~Lady Black~
Even I thought of the World Cup levitation debacle! I will need to read the book for accurate assesment..but hey, the muggles were really high don't you think, like 50 feet in the air and in OotP/HBP we have only seen them rise upto a few feet at best.
But then again, maybe it was the combined use of the spell by a dozen or so crazed bigots.
Coming to the spell itself, well, its not suprising that the DE's know it since it was invented by Snape.
As for Luna, well, its quite possible that she came across the spell in some of her weird random wandering through her books or at her home.
The spell seems easy enough to do, not requiring much concentration or strength of will...so just like Harry, she might have had the spell in the back of her mind and used it at the spur of the moment.
I didn't think much of it...just thought that it was cool that they were actually using spells from the books themselves, and not inventing some new ones of their own as they often do!