No. I didn't know it either and nor did various bookish friends inc Mark.
I was looking up something about the psychology of love, as part of a paragraph in my book, and found this word. It actually means the state of euphoria and what we consider 'falling in love' when you meet someone . . . hot, so to speak, or actually, beyond hot: you might feel moved to write poetry, send locks of hair/red roses etc . . .
Apparently it's gauged to last about six months: then the offensive socks, annoying whistling in the bathroom stuff kicks in. Either it can blossom into true lasting love at this point, or withers away into intolerance and looking at other hot people.
Anyway, I think it's a beautiful word and am happy to have made it's acquaintance.