Ah, the adder – a creature and a name that might well be called a subtracter. Why? Reasons multiply, but first of all it’s how the word divides.
What am I nattering about? Oh, put on an apron, cut yourself an orange, and have a seat, and I’ll explain it. Let’s start with the genesis of the thing – specifically, Genesis 3:4, where, in Ælfric’s version, it says, “Ða cwæð seo nædre eft to ðam wife: Ne beo ge nateshwon deade.” Ah, how English has changed in a thousand years. Now we would say, “Then the snake said to the woman, ‘You will not surely die.'” You may recognize cwæð as cognate with quoth. Quoth the snake… But do you see what word in Old English meant “snake”? It’s nædre, which was also spelled næddre and quite a few other ways, including nædder.
But just as the snake in Genesis lost its legs and so reached its nadir (in German, sein Niedergang), the English nædder – become nadder – lost its n. Well, OK, that’s not really true. It’s just that a nadder became an adder – the same shift that took the /n/ off the beginning of apron and orange. So the change in division resulted in a subtraction.
We see that in Old English, nædre referred to snakes generally (and also in particular to the evil snake in Genesis). Here again we have seen over time some subtraction – and multiplication. Our current word adder does not refer to all snakes (just as our current word deer does not refer to all wild animals, as it once did), but it also does not refer to just one kind of snake. It’s used for any of quite a few different venomous vipers from various parts of Europe, Asia, and North America, as well as some unrelated venomous snakes from Southeast Asia and Australia, and some harmless North American hog-nosed snakes. All but the hog-noses have another good reason to be called subtracters: if they bite you, they may well subtract you from the living. They surely cause dread in those who have dared to mix it up with them.
And, thanks to metaphor, we add one more way in which adder refers to a subtracter: that deceitful, treacherous, malicious kind of person – the sort I’m more used to hearing called a snake, for the same reason. We may also add some compounds and collocations: adder-deaf, or deaf as an adder, because one kind of “adder” was thought to be deaf; adder’s mouth, a kind of orchid; adderbolt, a dragonfly; adder’s tongue, a kind of fern; and adder-tongued – which takes us back to that sort of person the addition of whose presence is a subtraction of civility. You know, those types whom we wish were nonplussed more often. Ah, their nasty lies – if only Eve had eaten an orange instead.