Criss-Cross (1475) originated from the Middle English Christ's-Cross, and earlier, 1390, from Cros-Kryst, was the mark + or X written before the alphabet.
This originated from the Greek spelling of the name of Christ, which were X P, called "chi-rho." This is the origin of the use of X-mas for "Christmas."
During Medieval times when many were illiterate, an individual would mark their name by the X, the Christ's Cross, and kiss it in front of witnesses to show sincerity. This was a written form of the oath, "So help me God." This was also the origin of signing Valentine cards with XXX and OOO, to represent kisses.
Learning the "Criss-Cross Row" was the expression used for learning the alphabet. The mark stood for an invocation said before reciting the alphabet:
<Christ-cross me speed ("May Christ's Cross give me success").>1475CC001
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American Quotations by William J. Federer, 2024, All Rights Reserved, Permission granted to use with acknowledgement.
Endnotes:
1475CC001. Criss-Cross, 1475. Victoria Neufeldt, editor, Webster's New World Dictionary of American English (New York, NY: Simon & Schuster, Third College Edition, 1988), p. 328. Gary DeMar, God and Government-A Biblical And Historical Study (Atlanta, GA: American Vision Press, 1982), Vol. 1, p. 18. John Keats, Life and Letters, I. 112, (1818). Robert K. Barnhart, editor, The Barnhart Dictionary of Etymology (Bronx, NY: H.W. Wilson Company, 1988), p. 235. J.A. Simpson and E.S.C. Weiner, editors, The Oxford English Dictionary (Oxford, England: Oxford University Press, Second Edition, 1989), Vol. 2, p. 29. David B. Guralnik, General editor, Webster's New World Dictionary of the American Language-Concise Edition (New York: Rand McNally & Company, The World Publishing Company, 1966) p. 180.