Why would a book have a leaf in it? I know, it must be being used as a bookmark – a left-field, unconventional type of bookmark. Yes, a bookmark that rails against the expectations of society, absolutely sticking it to the man like it’s a leaf of paper on which the message “kick me”, or some other more imaginatively profane thing, has been written.
So, to metaphorically take a leaf out of someone’s book is to be a bit ridiculous and nasty, because doing that thing would leave the book’s reader a bit inconvenienced, all of a sudden no longer quite sure how much of the book they have read. It seems like a rather silly thing to do, something that might seem quite pukka in the heat of the moment but would soon be sorely regretted. I can imagine that, if someone had to go through the humiliation of getting strapped to their back a piece of paper on which “kick me” (or some other more imaginatively profane thing), they might become hot and bothered and act childishly and enjoy their slice of revenge quiche by removing a bookmark from the culprit’s reading matter. Cheeky – they won’t be doing that again!
I don’t think there’s much wrong with using a leaf as a bookmark. It’s quite a good idea, and not just when it seems the only alternative to blasphemously folding the corner of a page or – yikes – leaving a pamphlet open to face a flat surface. I don’t imagine that a leaf would be abnormally vulnerable to being taken out of a book. In fact, an expensive leathery sort of proper bookmark would, by contrast, invoke all sorts of jealousy – an absolute liability.
Grabbing a natural leaf straight from a tree doesn’t involve all sorts of processing at great cost to the environment and stuff like what a proper bookmark does, drastically slashing the carbon footprint, probably. Furthermore, the choice of the word “a” rather than “the” implies that there would be multiple leaves left at different points in the book, making thriftiness more paramount than ever.
If the leaf is a tea leaf, I can see how at first that might seem convenient, because tea is a popular beverage – but these days the “leaves” tend to be soggy piles of dust, locked inside damp paper, crumpled up like that other inappropriate candidate for use as a bookmark, cooked spinach. (Cooked spinach is spinach in its worst form, obviously. I do actually enjoy all spinach, but cooked spinach doesn’t count as spinach.)
Reusing a bay leaf can be even more dangerous for the same reasons – the gentle stain of weak tea might be OK, but nobody wants to smear lentils all over their book. (Lentils are commonly included in dishes that also call for bay leaves, although that is a broad generalisation.) Even decadently using a virgin leaf raises questions about sap and stuff. Best to use a dried one. That, presumably, is the standard leaf to use, the one recommended by professionals. Yes.
Oh. “Leaf” can mean “page”. Of course it can. It’s an archaic tradition, probably retained from when they hadn’t invented paper yet, so had to use big stones. That makes perfect sense. I suppose they call it “heritage”, and yes, I suppose that is a thing that is nice sometimes, and it’s healthy to remember that writing something used to involve chisels and all sorts of palaver like that, so we mustn’t take laser printers for granted. But it is also frequently confusing to small people like what I was when I came across the expression. Nobody – yes, nobody – uses the word “leaf” instead of “page” in any other situation.
The thing, however, is that my point still stands – quite a lot more so, in fact, than it would in a world in which leaves really were used, maybe on a regular basis, by readers of books who want mark their place in a book. If a bookmark is removed, it doesn’t take especially super powers to estimate how much has been read – bookmarks slide out all the time, and it’s not the end of the world. Now, while the stain left by a damp tea leaf might be annoying, it’s still possible to put up a fight and read the distressed page, maybe wipe off some of the lentils with a damp cloth. If, on the other hand, a page has completely been ripped out, there’s nothing you can do about it. Sure, I’m flattered that you are looking up to me, that I’m your idol, but you’ve ruined my book. Why couldn’t you use a photocopier? (Please ignore the copyright implications.) I would certainly use a photocopier. You ought to take a leaf out of my book. (Yes.)