today's adventure in etymology

This morning, while idly pottering, it suddenly occurred to me that I knew two facts I had never previously put together (or at least, if I had I'd promptly forgotten):

1. peanuts are called pea nuts; and
   
2. peanuts are a legume: which is to say, speaking imprecisely, a kind of pea.

This abruptly recontextualised for me recipes in which peanuts are boiled (e.g.), and also their general shape (including their shells! but also what they do when you split them!).

I did, of course, go and double-check the etymology -- which led me on to:

a false singular from Middle English pease (plural pesen), which was both single and collective (as wheat, corn) but the "s" sound was mistaken for the plural inflection. [etymonline]

... and that is why I am daydreaming happily of asking someone sputtering in outrage about singular they Their Thoughts On Peas. Thank you and goodnight.