WOTD: Plumb

It’s been a little while since my last WOTD; perhaps a better acronym would be WOTW or even WOTM. But as often happens, I was recently asked whether I knew anything about the origin of the word plumb — not the fruit; that’s plum — and as most often happens, I do know something.

Plumb is one of those surprisingly useful words. It can be a noun, adjective, adverb, and verb, with a range of apparently unrelated meanings — apparently unrelated, but as we’ll soon see, in fact connected by a central metaphor. As a noun, a plumb is a simple tool: a weight fixed to one end of a line. It’s used to determine depth or verticality. For depth, one drops the weighted end of the line in and lowers it until the weight touches the bottom; the length of the line meted out at that point is the depth of the hole, water, or what have you. To establish verticality, one simply lets gravity pull the weighted end downward, then one marks the line. Why is it called a plumb, then? The word comes from Old French plomb(e), in turn from Latin plumbum “lead”. If you remember your Periodic Table of the Elements, you’ll know that the symbol for Lead is Pb (= Plumbum). A plumb line is so called because the weight attached to one end is usually a small lead ball.

The word and some of its compounds (e.g., plumb bob, plumb rule, or plumb line) goes back at least as far as Chaucer. In his late 14th-century Treatise on the Astrolabe, he describes “a plomet hangyng on a lyne” as well as the use of “a plom-rule” “[t]o fynde the lyne meridional to dwelle fix in eny certeyn place.” The word also appears in the Promptorium Parvulorum, the first English–Latin dictionary (compiled in 1440).

Because one use for a plumb is to determine depth, the verb to plumb eventually took on a metaphorical shading, “to explore the depths, to examine, to probe” — as in “to plumb the limits of human understanding”. And because another use for a plumb is to determine verticality with precision and exactitude, an adjectival and adverbial use developed, meaning “perfect(ly), exact(ly), complete(ly)” — as in “plumb center”, “plumb crazy”, or “plumb done in”. This usage is generally more colloquial, regional, or rural.

Let me close by calling your attention to two or three related words. Everyone knows what a plumber is, but most people don’t realize that plumber and plumbing derive from an underlying reference to lead — as in a pipes made out of that metal. Lead for our drinking water?! Perish the thought!

And how about the verb, to plummet, meaning “to drop downward rapidly” — just as a lead weight does! And finally, the colorful noun, aplomb, meaning “confidence, poise, skill” — the very opposite of leaden, isn’t it? But it comes to us from the French à plomb “perpendicular” — perpendicularity, naturally, being a measure taken with a plumb.

So, till next time, I hope y’all found this post plumb int’resting. (Did I really just write that? *groan* :)