Looking up something else in my Merriam-Webster, I ran across ridley, the name of two varieties of sea turtle. What struck me was the conjunction of the etymology and the date, respectively “unknown” and 1926. There are lots of words with unknown etymologies, of course, but you’d think that recent a word would not be a total mystery. Wikipedia, in its Kemp’s Ridley article, says:
These turtles are called Kemp’s Ridley because Richard Kemp (of Key West) was the first to send in a specimen of the species to Samuel Garman at Harvard. However, the etymology of the name “Ridley” itself is still in question. Prior to the term being popularly used (for both species in the genus), L. kempii at least was known as the “bastard turtle”.
I wonder if the OED will turn up anything more when it gets to this word in its ongoing revision?