Have I told you that Bill has built a whole entire bar* in our house? It’s gorgeous, and he stands behind it and nods “whuddullyahave?” at you and it’s awesome. He uses lots of fresh citrus in his drinks, and the other day he encountered, and showed me, an orange of unusual pith. And it was not until that very moment that I’d ever thought to check on the connections between “pith” and “pithy” and “pith helmet”… and, as always, I can’t imagine that I’d gone about the world not knowing this. Because: it involves conjunctive plant tissues, bovine spinal cords, the Bengal Spongewood, and a too-good-to-be-true Greek coincidence (hereafter, a “grecoincidence”). Here we go!
Ok: pause. Remember that in the 1934 Webster’s International, the earliest definitions appear first, even if obsolete. So what we get to see here is the figurativization-journey of “pith,” from “living spongy stuff” to “the living spongy stuff in the middle of a thing” to “the centrally important, life-forciness of a thing.” So amazing! And, also, kind of gross: all this about bone marrow and the spongy interior of hair, right? Bleah.
Yeah, so then there is the verb, here to say “Oh, I’ll show you gross” :
So, that’s a thing you can do. Just pass the wire or needle up and down the vertebral canal, you know. Which is the same thing as when Bill tidies up an orange peel before adding it to my Negroni! What a world a we live in, honestly.
Now you are no doubt wondering: Does this mean that “pith helmets” were made to protect European colonizers’ heads from the “spongy interiors” of the land, animals and people they were brutally, bloodily subjugating?!
No…but also yes, I think we all know perfectly well.
A little more detail comes from the Online Etymology Dictionary (OEtD), always a nice supplement to my 80 year old dictionary:
pith (n.)
Old English piþa “pith of plants,” also “essential part,” from West Germanic *pithan- (cognates: Middle Dutch pitte, Dutch pit, East Frisian pit), a Low German root of uncertain origin. Figurative sense was in Old English. Pith helmet (1889, earlier pith hat, 1884) so called because it is made from the dried pith of the Bengal spongewood.
Here we get the nice specific Bengal spongewood, and we also get that “pith” is connected to “pit”! (But just the “hard seed” kind of “pit.” Not the “hole or cavity” kind…and if you want to really blow up your brain: those two senses of “pit” are not etymologically connected. Check it out here!)
Ok! So that’s how we get from dicotylodenous conjunctive tissue to spinal marrow to vigorous words. And yes, let’s get into words, into “pithy,” shall we?
So what’s funny here is that the “spongy tissue” definition is first, hence “earliest,” but the OEtD says the figurative use came first: that it went definition 2 (1520s), then 3, then 1 (1560s). Anyhoo: 3 is basically how we use it now. In my head, there is also the mildest flicker of potential derision–as in, yes, “pithy” means “substantive and meaningful….yet brief!” but because that’s a teensy bit of an overly(-self-)congratulatory accolade, I think it could be used to throw shade. “Pithy gall” seems to have no related meanings, but I love it too: like “how dare you say that, and how dare you say it so cogently.”
And all this brings us to the Great Grecoincidence, which I just can barely handle.
So, I found this, read the definition first, and was like “ha! cool! A whole –ology based on being pithy.” AND THEN I looked at the origins, and just fell right down, because it has nothing whatever to do with spongy interiors or life forciness. And in this entry, it sounds great: persuasive! Nothing wrong with that. But, it seems the actual OED adds something after “persuasiveness”: “the use of specious or plausible arguments.” (“plausible” here meaning “deceptively believable”). And, the examples:
1615 Byfield Exp. Coloss. ii. 4 Pithanology, which the apostle condemns, is a speech fitted of purpose, by the abuse of rhetoric,..to please and seduce. 1650 Trapp Comm. Deut. xiii. 3 Hereticks have their pithanology, their good words and fair speeches. 1730 A. Collier Clavis Univ., Spec. True Philos. 127 Called also by its christian name of pithanology, or science, falsely so called.
So there you have it. If you want to genuinely acknowledge a speaker’s terse cogence and/or vigorous substantivity, compliment their pith.** If you want to throw shade: “Girl, that was some beautiful pithanology.”***
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*Or, “buil has Billt”! Anyway, it looks like this:

**We all are so worried about “his or her” and we feel bad and wrong when we use “their,” but I am here to tell you: this is how languages change. They lack some essential function, in this case a way to name non-gendered 3rd personal singular possession (and they generally lack this for a reason; for example, in a patriarchal society, just using the masculine form tends to suffice in the written record, which often serves as a de facto prescriptive grammar), and when the need for that function becomes big enough, people just invent or appropriate a word to fill it. So say “their” if you want! Say it with intention and sociolinguistic grounding!
Update Dec 4, 2015: I’d like to acknowledge my cis-gendered Assness for not including that “they” is also needed to refer to gender non-conforming people. And none other than the Washington Post is ready to use it for that purpose and the one above! Read how and why here.
***Following “The Read,” “Girl” is applicable to a speaker of any gender identification. Are you listening to The Read yet?