One Thing Leads To Another
I love love love discovering something that I didn't know and then discovering that in fact I did in a sense know it: I just didn't know I knew it.
Yesterday I was reading Sarah Vowell's Assassination Vacation on the bus to work (you can dip into it here — god, I love Google Books so much) when I ran across this sentence from American President Garfield's commencement speech to his alma mater in 1880:
It has occurred to me that the thing you have, that all men have enough of, is perhaps the thing that you care for the least, and that is your leisure — the leisure you have to think; the leisure you have to be let alone; the leisure you have to throw the plummet into your mind, and sound the depth and dive for things below.
"Throw the plummet into"! That means that "plummet" can be used as a noun, and not just a noun derived from a verb (and therefore synonymous with "a fall" or "a drop"), but a solid, objective sort of noun, a noun that names something you can touch and feel.
I did not know this. But a moment's reflection brought me down this path: A plumb is a weight of a sort, the name deriving from Latin "plumbum" (as I already knew, having written about it some time ago), which is their name for "lead" (the metal, that is) via French "plombe", which they to this day use for the metal. Therefore, "plummet" can only be the diminutive form of "plumb": "plumb-ette". Therefore (and you will have to imagine my immense delight at realizing this fact), the verb must have derived from the noun which until a few seconds ago I never knew existed!
The noun "plummet" is very old indeed, dating from 1388 (as "plomet"). The verb meaning "to plunge rapidly", on the other hand, first entered print in 1939. And yet somehow in that short span of time, a few human generations, the verb has entirely taken over the word's life, and the noun has receded to the point that in all my forty-odd years of reading I have only just encountered it.
Oh, and while I'm at it, I might as well point out that "plumber", as will be obvious as soon as you think about it, derived from "plumbum", because pipes used to be made of lead, and likewise the system of pipes that carry our water is called the plumbing.