From the glossary at aestheticism.com:

"Yaoi is an acronym for 'yama nashi, ochi nashi, 
imi nashi': no mountain (ie peak; climax), no 
point, no meaning."

I've read this other places as well, but since I 
don't speak Japanese I can't really confirm.  It 
supposedly pokes fun at the fact that most yaoi 
has no real plot, and tends to put together 
characters who make little sense as a couple. 
(Now, having 160 Escaflowne doujinshi, a large 
number of them yaoi, *that* I can confirm! Folken 
and Allen? As if!)

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The Lizzard