Vocabulary in A Connecticut Yankee in King Arthur's Court

A palimpsest is a manuscript whose pages have obviously been scraped clean of prior text so that the pages can be reused.  When "paper" was made of vellum (calfskin or sheepskin), which was expensive to make and durable, manuscripts were often used multiple times.

Parchment is paper made usually of calfskin or sheepskin, very typical of manuscripts from the medieval period and very expensive.

A "hauberk" is a tunic of chain mail, usually backed by padded leather and cloth.