The Etymologicon: A Circular Stroll through the Hidden Connections of the English Language

Mathematics

Mathematics is an abstract discipline of such austere beauty that it’s often surprising to find that its words and symbols have dull, concrete origins. Calculus is a formidable word that loses some of its grandeur when you realise that a calculus is just a little pebble, because the Romans did their maths by counting up stones.

Oddly, an abacus, which you might reasonably have expected to mean little pebbles, comes ultimately from the Hebrew word abaq meaning dust. You see, the Greeks, who adopted the word, didn’t use pebbles; instead they used a board covered with sand, on which they could write out their calculations. When they wanted to start on a new sum, they simply shook the board and it became clear, like a classical Etch A Sketch.

Average has an even more mundane explanation. It comes from the Old French avarie, which meant damage done to a ship. Ships were often co-owned and when one was damaged and the bill came in for repairs, each owner was expected to pay the average.

A line is only a thread from a piece of linen, a trapezium is only a table, and a circle is only a circus. But the best of the mathematical etymologies are in the signs.

People didn’t used to write 1 + 1, they would write the sentence I et I, which is Latin for one and one. To make the plus sign, all they did was drop the e in et and leave the crossed +. By coincidence, ET also gave us &, and you can see how t became & simply by messing around with the typefaces on your word processor. Type an & and then switch the font to Trebuchet and you’ll get , to French Script MT and you’ll get , to Curlz MT and you’ll get , Palatino Linotype and you’ll get and finally, as this book is printed in Minion, you get .

Most mathematics used to be written out in full sentences, which is why the equals sign was invented by a sixteenth-century Welshman who rejoiced in the name of Robert Recorde. Robert had got thoroughly bored of writing out the words is equal to every time he did a sum. This was particularly irritating for him, as he was writing a mathematical textbook with the memorable title, The Whetestone of Witte whiche is the seconde parte of Arithmeteke: containing the extraction of rootes; the cossike practise, with the rule of equation; and the workes of Surde Nombers.

But the prolixity of the title was matched by the brevity that the book brought to algebra. Recorde wrote:

… to avoid the tedious repetition of these words: is equal to: I will set as I do often in work use, a pair of parallels, or Gemowe lines of one length, thus: , bicause no 2 things, can be more equal.

So is an equals sign because the two lines are of equal length. Robert Recorde published his Whetstone of … (see above) in 1557 and died in debtors’ prison the following year, thus demonstrating the difference between good mathematics and good accounting.

Recorde thought that the two lines of were so similar that they were like identical twins, which is why he called them gemowe, meaning twin. Gemowe derived from the Old French gemeaus, which was the plural of gemel, which came from the Latin gemellus, which was the diminutive of Gemini.