(Christ-cross row). The A B C horn-book, containing the alphabet and nine digits. The most ancient of these infant-school books had the letters arranged in the form of a Latin cross, with A at the top and Z at the bottom; but afterwards the letters were arranged in lines, and a + was placed at the beginning to remind the learner that “The fear of the Lord is the beginning of wisdom.”
Mortals ne'er shall know More than contained of old the Chris'-cross row.
Tickell: The Horn-Book.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894