Wait, how do I pass a Litmus Test?
The word litmus has two possible etymologies: the first possibility litmose comes from the Old Norse combination of litr meaning color and mosi meaning moss. For the Norse, the lichen Roccella tinctoria was used for dying clothes. Ernest Weekly’s Etymological Dictionary of Modern English goes as far as to identify a probable time and date that the word entered English: around 1300 from Norway via the port town of Lynn. The Oxford Universal English Dictionary offers the Middle Dutch word leecmoos or lijcmoes from a combination of the Hundustani word lac (from which we get our word lacquer) meaning a dark red incrustation shed by certain insects and moes, meaning pulp. The OUED does offer the Old Norse as a related derivation.
Litmus was first identified for scientific use by Robert Boyle (Happy Birthday, Robert, born on this day, January 25, 1627) -when he identified paper treated with crushed and prepared leaves from the lichen. The resulting light blue paper will turn red in the presence of acid and back to blue in the presence of a base. The first figurative use of ‘litmus test’ not seen until the 1950s. Today ‘litmus test’ has as much political use as it does scientific use, and the current administration is applying a strict anti-climate litmus test for federal employees. Contact your Congressional Delegation if you think SCIENCE should be above simple litmus tests: https://www.congress.gov/contact-us
Image of roccella tinctoria courtesy of Leif and Anita Stridvall. You can see more of their fantastic gallery of all things plant related here: http://www.stridvall.se/la/galleries.php
