What Did X Stand For Before X-rays?

Alphabet books have been with us almost as long as the printing press, because children need to learn their letters. But x-rays have only been around since 1895, and the xylophone wasn't widely known by that name until the 20th century. Illustrating the letter X before that was a challenge, one that was approached in several different ways. While A is for apple and B is for bear, ball, berry, baby, and any number of everyday things, it was quite a stretch to use an X. The Persian king Xerxes and Xanthippe, the wife of Socrates, got into way more books than they deserved because of their names, as did Xanthus and St. Xystus (which is more often spelled Sixtus). Some early readers used "expensive" or "axe," which is cheating. Others just threw their hands up, like the page shown above from an 1830 alphabet book, which appears to hope no one notices. See a roundup of the treatment of X before x-rays at the Public Domain Review. -via Metafilter