What even is a rook?

What exactly is a chess piece?

One time, in the sixth grade, a friend and I were about to play a game of chess, but a bishop was missing, so we took an angel trinket from his mom's shelf and used that instead. It looked very strange but nothing about the game itself changed. It could have been a penny or a pebble or a peppercorn. Players often use an inverted rook to stand for a new queen without causing any confusion.

What exactly is a chess piece then? Like all of chess it is an abstraction. Its essence is a set of possibilities: its potential: its power. If you imagine a knight on an empty board and highlight all of the squares to which it could jump, that would be a better visual representation of its power than the torso of a horse. For the sake of convenience, however, we've all agreed that a horse torso symbolizes that particular set of radiating power. We could replace it with a frog if we wanted or even make it disappear altogether, as we do in a blindfold game, as long as the essential power remained. In the same way, the abstract number three can be represented by various numerals like III, ٣, or 3.

We're accustomed to having eight identical pawns on each side because they have identical powers, even though initially they have different values: rook pawns cover fewer squares than other pawns and central pawns cover more important squares. Of course a rook pawn can become a knight pawn after a capture and a bishop pawn often becomes a central pawn, so it's not an inherent value of the piece, but a result of its location, just as a knight on the rim is dim. Yet there's no reason we couldn't have eight different looking pawns, so that a c-pawn would look different from an h-pawn. In that case, if a pawn queened on the c8 square you'd know instantly where it started the game without having to backtrack in your mind. I face my knights at each other in the starting position, primarily because I like the way it looks and feels, but it's also amusing to me to always know which knight is which.

Chariots, cannons, ships, elephants, and towers

Of course knight-power was not always associated with a horse, just as queen-power was not always associated with feminine royalty, and rook-power did not always seem like a tower. In fact, the word rook derives from the Persian رخ rukh, which means chariot. Despite the fact that the tower-shaped piece has become ubiquitous in chess, it is still called a chariot in Chinese (車 jū), Vietnamese (xe), Mongolian (тэрэг tereg), Malayalam (തേര് theru), Estonian (vanker), and Georgian (ეტლი etli).

It is known as a cannon in Azerbaijani (top), Bulgarian (топ), Serbo-Croatian (топ), and Macedonian (топ), a ship in Armenian (Նավակ navak), Belarusian (ладзьдзя ladździa), Bengali (নৌকা noukā), and Thai (เรือ reūa), and an elephant in Hindi (हाथी hāthī), Kannada (ಆನೆ aane), Marathi (हत्ती hātti), and Telugu (ఏనుగు ēnugu). In most other languages, however, it is known as a tower or castle, and even though its form is arbitrary, we have a strong association between the power of a rook and a turreted fortress.

The Scacchia Ludus by Hieronymus Vida

Even before I started playing chess I was fascinated as a classicist by the poem Scacchia Ludus written in the 1500s by the Italian bishop Marco Girolamo Vida, a.k.a. Hieronymus Vida (1485?-1566). The poem is a mini-epic (or epyllion) of about 700 Latin hexameters, the poetic meter used for war stories, which narrates a chess game between Apollo and Mercury. For the poem he invented a goddess of chess, Scacchia, who would be the inspiration for Caïssa in the poem by William Jones in 1763. Vida wanted to avoid making up neo-Latin words so he called the rooks propugnacula—the tangible ramparts or towers of an arx or fortress—with high walls (altis muris):

tum geminae velut extremis in cornibus arces
hinc atque hinc altis stant propugnacula muris,
quae dorso immanes gestant in bella elephanti.

Then like twin fortresses in the far corners
Here and there stand towers with high walls
Which huge elephants carry on their backs to war.

The image of towers carried into battle by elephants is a curious one. Perhaps Vida is including or alluding to earlier traditions in which the rook was instantiated as an elephant, traces of which are still found in languages such as Hindi, Kannada, Marathi, and Telugu. It's also possible that he was thinking of the Battle of the Hydaspes, in which Alexander the Great defeated King Porus on the Indian subcontinent in 326 BC. The Greek historian Arrian tells us that Porus had 200 elephants in his army, and that after the Indian soldiers were routed they fled to the elephants "like a friendly wall" (ἀλλὰ κατηρράχθησαν ὥσπερ εἰς τειχός τι φίλιον τοὺς ἐλέφαντας, 5.15.2). The Greek word τειχός can be used not only of walls, but also of places protected by walls, such as fortresses and castles.

In any case, this seems to be the inspiration for the modern shape of the rook as well as the term castling, and so these three lines of Latin poetry shaped profoundly how we experience the game of chess to this day.