Sometimes I’ve thought this must just be for people to make story/storey puns. I mean, floor works just fine, doesn’t it? We all understand what it means in context, and every floor has a floor, so there’s a logic to it. Why even bother with storey?
I’m glad you asked. You’d probably guess, especially as storey and story are spelled differently, that the resemblance is purely coincidental, and they both had independent etymologies.
You’d think that, wouldn’t you, but in fact, the two could hardly be more closely related. There’s no exact record of when storey began to be used to refer to the floor of a building, but the generally-held belief is that it came about in the Middle Ages when many buildings featured painted windows or walls, which featured characters engaging in actions from one scene to another, in what could be described as a narrative. Or…what’s that other word? Oh yes, a story!
Story was already spelt as it is now at that time, so presumably the E was added to clarify that it was being used in the context.
So, if you had a building with three floors, and each one had a painted narrative on it, you could say your building was three stories high. Sometimes the… story of a word is just that simple.
Of course, putting on my teacher hat, I realise that storey and floor aren’t completely interchangeable. You can say that you live on the third floor of a building, but you wouldn’t say that you live on the third storey. Equally, you could say you live in a two-storey house, but not a two-floor house. You might say the house has two stories, but you’d still be much more likely to say that it has two floors.
This is what we call collocation: the tendency to use certain words alongside certain others, even when we could easily use other words in their place. There’s no particular reason we say heavy rain, for example, and not strong rain, or thick rain. The rain’s not actually heavy, but the term has stuck, and we can’t change it now.
It’s like that with floor and storey. There’s no grammatical reason we can’t say a two-floor house, or I live on the third storey. They just sound strange because we’ve just got used to using floor and storey in that way.
Of course this is something most of us never really have to think about, but from a teaching perspective it’s interesting. These are the kind of things that come up when students ask you questions, and are odd and specific enough that they’re not really covered in textbooks. You just have to figure them out yourself by looking at how we use language, and thinking about it, spotting the patterns.
Luckily for me, I’ve always enjoyed doing that!