Etaoin shrdlu


Etaoin shrdlu is a nonsense phrase that sometimes appeared in print in the days of "hot type" publishing because of a custom of type-casting machine operators to fill out and discard lines of type when an error was made. It appeared often enough to become part of newspaper lore - a documentary about the last issue of The New York Times composed using hot metal was titled Farewell, Etaoin Shrdlu - and "etaoin shrdlu" is listed in the Oxford English Dictionary and in the Random House Webster's Unabridged Dictionary.
It is the approximate order of frequency of the 12 most commonly used letters in the English language.

History

The letters on type-casting machine keyboards were arranged by descending letter frequency to speed up the mechanical operation of the machine, so lower-case e-t-a-o-i-n and s-h-r-d-l-u were the first two columns on the left side of the keyboard.
Each key would cause a brass 'matrix' from the corresponding slot in a font magazine to drop and be added to a line mold. After a line had been cast, the constituent matrices of its mold were returned to the font magazine.
If a mistake was made, the line could theoretically be corrected by hand in the assembler area. However, manipulating the matrices by hand within the partially assembled line was time-consuming, threw an operator off their pace, and presented the chance of disturbing certain important adjustments. It was soon realized that it was much quicker to fill out the bad line and discard the resulting line of text, then redo it properly.
To make the line long enough to proceed through the machine uninterrupted, operators would finish a faulty line by running a finger down the first columns of the keyboard, which also created a pattern that could be easily noticed by proofreaders. However occasionally such a line would be overlooked, and make its way into print.

Appearances outside typography

The phrase has gained enough notability to appear outside typography, including:

Computing