The haggadah (several copies that I've looked at, so I'm assuming this is universal?) tells us when eating certain foods at the seder to recline or lean to the left. I understand why we lean (the haggadah tells us that), but why the left in particular? Is this because of historical practice (maybe couches were asymmetrical)? Is there a symbolic reason? Some other explanation?
I'm asking why the haggadah has this instruction; while later interpretations of what it means may be interesting, that's not my question.