As to 70's and 80's programmers knowing about printing presses I'll point out that a significant early AI program (1968-1970) was named SHRDLU. One familiar with printing history might recognize those letters as part of the second column of moveable type characters on a Linotype machine (and other type-casting machines.) I didn't look up a reference, but I recall that the first row of bins for hand set hot type letters followed the same convention of letter frequency in English text (for english speaking countries that is.)
etaoin shrdlu
That string of characters became more well know due to its appearance in hot type set news papers of the era. The characters sometimes accidentally made it to press rather than being pulled as part of an erroneous line of text.
https://en.wikipedia.org/wiki/SHRDLU https://www.wikiwand.com/en/Etaoin_shrdlu