Q From Megan Dannenfeldt: What is the origin and definition of the word watershed?
A What it means depends on where you’re standing, since North Americans mean something different by it than do people from other parts of the English-speaking world.
It first turns up in English near the beginning of the nineteenth century. It was then purely a scientific term for an imaginary line that separates two river systems. Think of it as the ridge of a roof: which river system rainwater flows into is determined by the side of the line the rain is deposited on. This is the same idea as the German Wasserscheide from which English borrowed the word (what linguists call a calque or loan translation).
In English, the noun shed is the English equivalent of the German scheide, both of which have come down to us from the same Old German root. The English noun derives from the verb to shed. It’s an old word for a division, split or separation — a shed could be a hair parting, for example, and could also be used for a ridge of land separating two areas of lower country, a divide. (These days a shed is usually a simple building for shelter or storage; this is an altered form of shade, and so has no link to this other sense of the word.)
In North America, the word watershed often means not the dividing line, but the river catchment areas on either side of the ridge, the whole land area that drains into a particular river. How the sense shifted isn’t clear. It came into use only around the 1870s, and may have been a misunderstanding.
The difference in sense explains why Americans don’t use the figurative sense of the word as much as the rest of us do. That refers to an important point of division or transition, as in this sentence from the Daily Telegraph in June 1999: “The Balkans conflict is at a watershed between a diplomatic settlement and the prospect of a ground war”. This figurative usage only makes sense if you use watershed in its original meaning of a dividing line.