For those who thought it might be someone getting confused and/or a typo -- I was about to reply with a link to the thread where I first saw it, but i'm not going to bother. Search for "LJ" in the threads and you'll see it pops up in more than one place -- def not a mistake, just some under-represented position lingo.
Essentially I saw a hand or two where the OP would say "I had XX in the LJ and UTG limps....etc" or "I raise with XX from UTG+1 and LJ 3-bets" or something similar.