Many scholars have guessed at what the letters L, P and Q stand for. Some notable guesses from history are:
Labia Patting Queer -- Abraham Lincoln, 1857
Light Particle Quantum -- Albert Einstein, 1909
Long Poop Quelf -- Rosa Parks, 1955
Lusting Pony Quadriplegic -- Neil Armstrong, 1969
Lost Puppy Quencher -- Jane Goodall, 1982
Lynnea Patricia Quick -- Danielle Berndt, 2001
Lingering Picnic Queen -- Justin Bieber, 2010
Frank-"Hey, what does LPQ mean?"
Bill-"Haha! your so out of it! You don't even know what LPQ means! Haha, n00b!"