The problem: in the 1950s, how does a lexicographer find every English word ending in -graphy or -itis without a searchable database? Merriam-Webster’s answer was the backward index: type every entry in reverse alphabetical order, then re-alphabetize. The resulting card file (315,000 entries, typed by hand) is what let the dictionary’s etymology team catch suffix patterns the front-of-the-book ordering hid. Surfaced via Kottke.