My nautical archaeologist contact clued me into an amazing resource. The Jewish and Arabic scholar Shlomo Goiteim made his life's work the translation and understanding of a trove of medieval documents from something called the Cairo Geniza.
Jews believe, as many do, that the name of God is sacred. This extends to the written name: so any paper that might contain God's name is considered special. As a practical matter, any writing in Hebrew may contain the Name. At the very least, the characters YHWH would all appear in any writing of length. So even if out of order and separated, the Name is in there.
What to do, then, with personal letters, bills of sale, property records, lading bills, legal arguments, etc, etc? A special room in the medieval synogogue called the geniza was set aside as a repository. Eventually the documents would be interred to await the Resurrection. In Cairo, the geniza was a room with no doors or windows, with only a slot near the ceiling accessible by ladder. It was opened in the late 19th century and has been studied ever since.
This is one of those, to my Goyish way of thinking, quaint and wonderful bits of Jewish scholarly thought. One bit of logic leads to another, and then naturally one needs to construct a geniza!
It gives us a unique window on daily life in medieval times which is not available from any other subculture. The Muslims and Christians of course wrote things down, but their more casual writings are ephemera. For the Jews of Cairo in 1100 AD, everything went into the Geniza.