This word belongs to a small set of words that are virtually never spelled out in full, and many of those who know the abbreviation don’t even know the full form (videlicet is another; you probably know it as viz., if you know it at all). And, in its abbreviated form, ibid., it is (also like viz.) a tessera word.
What do I mean by tessera word? Say you get a coin in your change, and you don’t recognize it. You think it’s from some country you can’t identify, or perhaps it’s a token from some fancy arcade, and you don’t know what it’s worth, so you give it away, or you throw it away, or you put it somewhere, but you don’t use it, because you don’t know how or where to use it. But you see ones like it every so often, and people seem to use them, and everyone who uses them acts like everyone knows what they’re for. No one ever tells you. Eventually you get to know someone who invites you to join them somewhere – it could be a place that’s new to you, or it could be somewhere you’ve been before but they go to a different entrance than the one you’re used to – and they pull out one of those coins and put it in a slot and go in. Aha! At last you know. Well, a tessera word is like that.
A tessera is a token, or a password, or a token used as a password. Its name comes directly from Greek τέσσερα ‘four’, because originally tesseras were quadrilateral (i.e., rectangular, perhaps square; tessera is also used to refer to other square things, such as mosaic tiles). They were used for such things as the equivalent of a theatre ticket in the theatre. A tessera of hospitality was a ceramic piece broken in two, one kept by host, one by guest, to allow recognition (I’m fantasizing a circumstance where the parties are masked, but I suppose it could just be a matter of the host having a staff member let you in). And a tessera word is one that is known by an in-group, and knowledge of it allows you to function as part of that in-group.
That’s not to say that tessera words are pointedly kept as in-group knowledge. Often it’s just a matter of everyone who knows them assuming that those who need to know them will know them – which also means, though they might avoid reflecting on it, that the words are useful exclusionary devices.
Scholarly writing has an assortment of expectations and practices, and among the more exacting and exclusionary are the referencing standards. There are multiple standards you can follow, and while variations are possible within each standard, it is expected that you will know certain things. If I am reading a scholarly work and see “(Norris, Between 19)” I am supposed to know that it is using MLA style and that I should look into the list of works cited to find a work by an author whose last name is Norris and having a title featuring the word Between, and I will find the quoted material on page 19. And if I am reading a scholarly work (a different one, to be sure) and I see a footnote or endnote and I look at it and see “Ibid., 19” or just “Ibid.” I am supposed to know…
…do you know what you’re supposed to know? I didn’t when I first met it and for some years after. In fact, I assumed it was some oft-cited work, like the Iliad or the Aeneid or whatnot. Something encyclopedic, I guess, since it was lending support to all sorts of things. It sure would be nice to have a work like that that one could cite (and no, I don’t mean Wikipedia, try to avoid citing Wikipedia; it’s very useful but it’s not authoritative or a primary source – follow its citations in turn to find something you can use). And I’d happily put “scitur” for “it is known,” or “omnibus notum” for “everybody knows,” or “scilicet” for “obviously,” but the problem with those is that they are not known – almost nobody knows them – and they are not obvious. Whereas “ibid.” is at least broadly known among scholars.
It – ibidem – means ‘in the same place’. It’s Latin, of course. It means “just look up at the previous note and see what work was cited there, and that’s the one we mean here too.” In other words, “we expect you to know this already.” The point of it is to save space, so you don’t have to put even an abbreviated reference there.
But it’s a nuisance. It’s a nuisance not just because it has to be learned like any tessera word, and not just because you have to look up at the previous note (and sometimes there’s a stack of ibid.s several notes long, and if they’re footnotes you may have to flip back pages, and if it’s online you may have extra clicking to do), but because any change to the footnote order in revisions ruins it. It’s like if you’re having a conversation with someone who’s behind you in the line for the bar at a reception, and you don’t notice that they’ve moved on and you’re now talking to someone else, and maybe handing a drink to them too. Generally this means that if a book’s going to use ibid., the author should not use it at any point in the writing or revising process, and the copyeditor will go through once the footnotes are definitely not going to be revised further and put it in everywhere it’s needed.
Or, you know, just not put it in. The abbreviated forms of citations are not so horribly long, and they’re clearer too. The style manual that has most upheld the ibid. tradition, The Chicago Manual of Style, says the following in its most recent (17th) edition (chapter 14, section 34):
In a departure from previous editions, Chicago discourages the use of ibid. in favor of shortened citations as described elsewhere in this section; to avoid repetition, the title of a work just cited may be omitted. Shortened citations generally take up less than a line, meaning that ibid. saves no space, and in electronic formats that link to one note at a time, ibid. risks confusing the reader.
(Now let’s have a chat, can we, Chicago, about place of publication in citations…)
Of course, if we discard ibid., we’re left with a tessera word we can’t use anymore. Which is actually a good thing, since accessibility improves scholarship. But it does mean that people who are looking at older works that use it will have to find out what it means. Fortunately, they can always look it up.