ETAOIN SHRDLU. The New York Times had an obituary on November 16 for Carl Schlesinger, a longtime Times typesetter who helped make a documentary about the last day that the Times was printed using hot-metal type. That date was July 1, 1978. The article used the phrase “etaoin shrdlu”, which I had seen many times in my youth, especially in a Chicago Tribune column entitled A Line of Type or Two, where it appeared often as a break between items. “Etaoin shrdlu” has its own wikipedia entry.
The letters etaoin shrdlu made up the first two columns of letters on a Linotype machine. They were thought to be arranged in order of letter frequency. (Although the order has been debated, a recent study using a Google books corpus came up with ETAOIN SRHLDCU as the order, which is in agreement on the first seven letters, transposes R and H, transposes D and L, and lets C into the second group). If an operator made a mistake in a line of type, he would often cast a new slug rather than try to correct the type which had been set incorrectly in the line of type. He would signal that that line was erroneous and should be removed, by running his fingers down the first two two columns of letters, thereby filling out the line with the signal “words” etaoin shrdlu. He would then start over with a correct line.
Not every bad line was picked up in the proofreading process, so that the letters etaoin shrdlu appeared quite often in newspapers and became well-known.