Tootfinder

»The origins of the exact dimensions of Letter size paper are lost in tradition and not well documented. The American Forest and Paper Association argues that the dimension originates from the days of manual papermaking and that the 11-inch length of the page is about a quarter of "the average maximum stretch of an experienced vatman's arms."« 🤡
Source:

Paper size - Wikipedia

hmm someone on hacker news claims that letter-number-letter abbreviations like i18n for internationalization comes from stenography
which disagrees with the explanation i previously heard that it came from a sysadmin at DEC abbreviating someone’s long name to fit as a username https://en.wikipedia.org/wiki/…