http://www.reddit.com/r/Fencing/comments/3cfken/history_of_the_salute/
We managed to find a 1650's description of the salute from Besnard, among others. And there is a completely unsourced quote from castle saying that it has to do with kissing the crucifix on the guard of the blade and throwing flowers to ladies watching. But none of that really seems very solid.
One user /u/Perivane has suggested that it's related to the military "present arms". I also notice that Besnard explicitly described the removal of the hat, so maybe it's related to removing your hat as a sign of respect?
But does anyone have a good explanation why people started raising their sword as "reverence" or a salute, before duelling or sparring with swords?
A factoid I've heard passed around at the club, and heard it from more than one unrelated person is that you were honouring god.
The word "reverence" makes more sense in that context.
Have no source of it, only heard it by mouth, so it's everything but reliable source.