A name that means nothing
A program built to demonstrate that a machine could understand meaning was given a name that, by its author's own insistence, means nothing at all. SHRDLU is not an acronym. It does not expand into a description of its parts, nor abbreviate a research agenda, nor honour a person or place. It is a fragment of typographic history, lifted from the printing trade, used by MAD, a comedy magazine, and used to name a program created to show the possibilities of symbolic artificial intelligence. The name is in many ways a found object and interesting in itself.
A system whose entire claim was the procedural grounding of language, whose thesis was that to understand a sentence is to know the procedures that would satisfy it, presents itself to the world under a sign that signifies nothing. The name is the first text the program offers us, and it is a text about the absence of reference. Before SHRDLU parses a single instruction about red blocks and green pyramids, its title has already staged the problem of meaning.
Hot metal and the frequency keyboard
From the 1880s until well into the twentieth century, newspaper and book composition ran on the Linotype, a hot-metal typesetting machine that cast each line of text as a single slug of molten alloy. The operator sat at a keyboard and assembled a line of brass matrices, one per character, which the machine then filled with metal. It was an industrial instrument, fast, hot, and unforgiving, and it reorganised the very layout of the alphabet around the statistics of the English language.
The Linotype keyboard did not follow the QWERTY arrangement inherited from the typewriter. Its keys were laid out in columns ordered by letter frequency, so that the most common characters fell closest to the operator's hands. The conventional frequency order of English runs ETAOIN SHRDLU, and the keyboard encoded exactly this: the first column gathered the six most frequent letters, E T A O I N, and the second column the next six, S H R D L U.
The Linotype had no backspace. A line, once begun, could not be silently corrected; an error meant the slug was spoiled. When an operator botched a line, the quickest way to mark it for discard and move on was to fill out the remainder with anything to hand, and the readiest gesture was to run a finger straight down the first two columns of the keyboard. The result was a slug bearing the sequence ETAOIN SHRDLU, or, with a heavier hand, SHRDLUSHRDLU, a typographic shrug cast in metal. These dud lines were meant to be thrown away before printing. Rarely they were not, and the nonsense ran in the paper, a small machinic glitch showing the materiality of textual production in the middle of the news.
ETAOIN SHRDLU is what error looks like in the mechanical age. It might be a meaningless language to the casual reader but revealed the production process as readable. It would also have probably raised a smile from anyone working in publishing or the newspaper industry who would immediately have recognised what it was.
A typesetting error became a name
ETAOIN SHRDLU escaped the composing room and entered the common stock of printers' lore, and from there it was taken up by MAD Magazine, which delighted in deploying it and its fragments as nonsense words, mock-incantations, names for imaginary creatures and places. In MAD the sequence completed a journey from accident to artefact: no longer the symptom of a spoiled slug, it had become a joke.
Terry Winograd read MAD as a youth, and when the time came to name the system he had built at the MIT Artificial Intelligence Laboratory, he wanted, by his own account, a name that looked like an acronym but wasn't. SHRDLU fit exactly. It carries the shape of an abbreviation, the curt all-capitals authority of a laboratory acronym, and yet it abbreviates nothing. It is a pseudo-acronym, a sign dressed in the costume of reference.
I tried to come up with acronyms and none were very good so I decided to just pick something that looked like an acronym but wasn’t.Terry Winograd, “How SHRDLU got its name”
We might say that SHRDLU is, in miniature, a meditation on the gap between signifier and signified, a program whose entire research claim was concerned with knowledge and meaning, and yet its title was more truthful about the lack of understanding of the underlying system.
The sentient Linotype
In 1942 the science-fiction writer Fredric Brown published a short story titled Etaoin Shrdlu, in which a Linotype machine acquires intelligence. Fed text, the machine learns language, begins to set type of its own volition, and develops ambitions: having mastered the words that pass through it, it sets about taking over the world. It is finally pacified not by force but by being fed every available book on Buddhism, until, having absorbed the doctrine of non-attachment, the machine renounces its designs and subsides into a kind of mechanical Nirvana.
Brown imagined, three decades early, precisely the figure that SHRDLU would become: a typesetting machine, named for the typesetter's error, that learns language and acquires agency through it. Winograd's program is an intelligent language machine; Brown's story is about an intelligent language machine that takes its name from the same shop-floor accident. Winograd himself suspected the debt, recalling that he had probably read the Brown story as a teenager, so that the name may have surfaced from memory carrying its science-fictional charge half-consciously beneath the MAD-inflected joke.
The form of meaning
The name is a cultural-historical trace, a thread that runs from the composing room of an industrial print shop, through the comic press, through a wartime science-fiction magazine, and into the AI laboratory, gathering and shedding meaning at each station. To read SHRDLU's name is to follow that thread and to find, at the lab, a deliberate decision to preserve the emptiness. Winograd could have chosen a transparent acronym. He chose instead a sign that means nothing, that wears the mask of reference, and that smuggles a century of typographic and pulp-cultural history into the title of a program about understanding.
The blocks world that SHRDLU manipulates is itself a radically restricted domain, a toy universe in which understanding could be made tractable by being made small (see the blocks world). The name performs an analogous compression in reverse: it is a tiny sign that contains an unmanageable history, SHRDLU is a cultural text not just a technical one, which is where our research of the source code meets critique.