"There’s our secret sign, I tell you, our life story!
Does the bed, my lady, still stand planted firm? –
I don’t know – or has someone chopped away
that olive-trunk and hauled our bedstead off?"

– Homer

The Odyssey, Book 23, lines 227-230. Odysseus gives Penelope the secret sign to let her know that she is talking to her husband and not someone else. The sign is the story of how he constructed their bedroom and bed around an olive tree. The bed cannot be moved, he says, unless someone chops down the olive tree. This is why Book 23 is titled "The Great Rooted Bed."