While reading my 1000 words of Geologic Literature today I encountered a word with which I was unfamiliar: palimpsest.
According to the on-line Oxford English Dictionary the orginal sense of the word (when used as a noun) is as "Paper, parchment, or other writing material designed to be reusable after any writing on it has been erased. Obs."—this form dates back to 1616. By 1825 the word had evolved to mean "A parchment or other writing surface on which the original text has been effaced or partially erased, and then overwritten by another; a manuscript in which later writing has been superimposed on earlier (effaced) writing." By 1845 the word had also expanded to apply to "a thing likened to such a writing surface, esp. in having been reused or altered while still retaining traces of its earlier form; a multilayered record."
It has also been used (as early as 1876) specifically to refer to "A monumental brass plate turned and re-engraved on the reverse side. Cf. A. 2. Obs.". However, the most interesting uses to my mind are the geological senses of the word: "A structure characterized by superimposed features produced at two or more distinct periods." (1914) and "Of a rock structure: partially preserving the texture that existed prior to metamorphism." (1912). There are also geographical senses of the word: "Of a landscape or landform, esp. a glaciated topography or a drainage pattern: exhibiting superimposed features produced at two or more distinct periods."(1922).
It isn’t often that I encounter a word I don’t already know, and I find I rather enjoy it. There is something nice about being able to open a good on-line dictionary, paste in the new word, and be given not only the meanings, but dates for the earliest use of the word in that context that they could find. In this case I particularly like the development of the word over time first being limited to something humans make/use and re-use and then expanding to other categories. The rock record is full of instances where information is written upon pre-existing information to a greater or lesser degree. Our challenge, as geologists, is to correctly interpret each layer of information and take care not to confuse different layers of information with one another. Particularly when the layers of information may be recorded in so many varied manners.