The term “Cairo Geniza,” to the initiated, refers to a repository of priceless ancient texts found in 1896 in a synagogue in Cairo.
These texts are worn-out Jewish sacred writings as well as secular manuscripts discarded by their owners, Palestinian Jews of Old Cairo, and given to the synagogue in Cairo, called the Ben Ezra synagogue.
Ben Ezra is Cairo’s oldest synagogue, occupying the same site for a thousand years since its construction in the middle of the 10th century. (P 231, The Sisters of Sinai by Janet Soskice, 2009, hardcopy).
This practice of giving to the synagogue arose from the Jewish belief that sacred texts, like humans, are living things, and when they become worn out, they must be protected from profanation. They are thus given to synagogues. (P 12, Sacred Trash by Adina Hoffman and Peter Cole, 2011).
Fragments of the manuscripts from the Cairo Geniza were first discovered in 1896 by the two remarkable Scottish twin sisters, children of an enlightened Scottish lawyer, who had earlier, in 1892, discovered the earliest known copies of the Gospel written in ancient Syriac, the language spoken by Jesus. This is now called the Sinaiticus Palimpsest. (P 125, 213, and 220 Sisters of Sinai)
The manuscript that triggered the search for the Cairo Geniza was the one purchased from the Cairo market by the two sisters and brought back to Cambridge University.
It was identified by the leading Jewish expert of the time, Solomon Schechter, as the original Hebrew text of the book of Ben Sira, which had been missing for nearly a millennium and survived only in its Greek and Syriac translations (p. 11, Sacred Trash).
Both books cited here are worth reading if you like the Indiana Jones genre of adventure archaeology and the ancient histories of Old Cairo and the Sinai Monastery.