Why shrdlu?

Why "shrdlu"? If you look at the photograph on this page of the keyboard of a Linotype machine, you will notice that the second vertical columns of keys in the lower-case and upper-case sections carry the letters SHRDLU. Rather like QWERTY on the top row of keys on a normal computer or typewriter keyboard. Linotype machines were used to create the rows of metal types used in the printing process in what were known as the "hot metal" days. If a compositor made a typing error, they couldn't just press the "backspace" key. Instead they would just fill up the rest of the line by running their fingers down those two columns of keys, and then eject the faulty line of type and throw it away.
I first encountered the word in a cartoon by Emile Mercier in one of Sydney's afternoon newspapers. It showed a tram (streetcar) going to "Shrdlu Junction". Not then being familiar with its origin, I just imagined it was a nonsense word.
Apparently, it's meant to be pronounced "shirdlu", but I've got used to saying it as "shrudlu". Take your pick, I don't mind.
I was once told that Linotype machines had a different layout from normal office typewriters so that people trained on ordinary keyboards would have difficulty adapting to the completely different layout of the linotype machine, thus restricting the number of people who could do the linotype operator's job, and thereby preserving a "closed shop".
You can read about Emile Mercier and his cartoons at http://home.alphalink.com.au/~loge27/p_war_aus/Soc-Cu/pwar_aus_sc_emilemercier.htm

The photograph of the linotype keyboard is from http://amrys.devl.org/photo/printing/printing-Pages/Image6.html which appears to belong to the Massachusetts Institute of Technology. I hope to post one or more of his cartoons on this site when I can find copies of them and get the necessary copyright clearance. I seem to recall there are some in the end matter of one or other of the late David Keenan's excellent books about the history of the Sydney tramway system.