This has bothered me for a long time too. I would chalk it up to Lewis trying to be humorous.

In The Last Battle, Lewis points out that there are several undiscovered islands in the far western seas. . . perhaps Tumnus thought that the land of Spare Oom and War Drobe were islands in that unknown sea.

That being said, I still think Lewis was trying to do it for humor. . . and unfortunately, I think it just came across at looking rather silly (which is what usually happens when people try to be funny)

If you think about it, his entire engagement with Lucy started as deception, a charge thrown rather abruptly upon him. I think Tumnus could have spoken that way for humor, or even if he meant it genuinely, Lewis could have used those statements as a hyperbolic form of humor to contrast the cultures of Narnia and our world for the reader, not necessarily to provide an accurate portrayal of a Narnian's response to Lucy.

If you think about it, his entire engagement with Lucy started as deception, a charge thrown rather abruptly upon him.

I had never thought of that before, Balin. Playing the knave like he did could have been completely for show, and would have helped to put Lucy off of her guard.

I think it's a perfectly understandable, and quite funny, misunderstanding. I really don't see what you're getting at.

I also disagree with your interpretation of James McAvoy's delivery. Tumnus genuinely misunderstood, just as he did in the book.

“This is the land of Narnia,” said the Faun, “where we are now; all that lies between the lamp-post and the great castle of Cair Paravel on the eastern sea. And you—you have come from the wild woods of the west?” 

“I—I got in through the wardrobe in the spare room,” said Lucy.

“Ah!” said Mr Tumnus in a rather melancholy voice, “if only I had worked harder at geography when I was a little Faun, I should no doubt know all about those strange countries. It is too late now.”
“But they aren’t countries at all,” said Lucy, almost laughing.

I'd tend to agree with King Erlian's original post here... given that Mr Tumnus speaks perfectly fluent English, and owns a house full of numerous items of traditional furniture, it does seem somewhat of a stretch to imagine he wouldn't know what the terms "Wardrobe" and "Spare Room" meant (though one could argue that Lucy used the terms in an unfamiliar context with which he would not expect them to occur - i.e. in relation to her origin)

That all said though, since it's merely a set-up for an amusing joke, issues such as logic and continuity can easily be disregarded in my mind.

I also agree with King Erlian. Good points! I hadn't noticed that before about how odd it was for Tumnus to say that. I definitely think he would know what a wardrobe and spare room was. But I don't think Lewis really thought much about that when he wrote it. Like the others here, I think it's simply a set-up for a quick, cute joke.

I also agree on the difference between the way Book!Tumnus said it and the way Movie!Tumnus said it.

Book Tumnus was more, "War Drobe? Spare Oom? Oh dear. If only I had paid more attention in school. "

Movie Tumnus acts that way the first time Lucy mentions it. But the second time he mentions it, when they're about to walk away together, he says it more like: "Well, then, Lucy Pevensie from the shining city of War Drobe... " And it came across in a more teasing manner.

~Riella

I still don't see what the problem is. I suspect this is a classic case of fans reading the book too many times and imagining irregularities.

I'm sure Tumnus knows what a wardrobe is. He simply thought that was the name of Lucy's country. Why does it seem so impossible that Lucy's country would be called Wardrobe? There are real cities with much more unusual names.

(though one could argue that Lucy used the terms in an unfamiliar context with which he would not expect them to occur - i.e. in relation to her origin)

Exactly. Tumnus has just discovered an amazing creature that he probably thought existed only in myth. Then he asks the creature where it came from, the last thing he expects to hear is "wardrobe" and "spare oom." I'm sure Tumnus knows exactly what those things are. He just assumed they were also the names of her county and city.

I'm sure Tumnus knows what a wardrobe is. He simply thought that was the name of Lucy's country...Tumnus has just discovered an amazing creature that he probably thought existed only in myth. Then he asks the creature where it came from, the last thing he expects to hear is "wardrobe" and "spare oom." I'm sure Tumnus knows exactly what those things are. He just assumed they were also the names of her county and city.

Thing is, if he knows what a wardrobe and spare room are, why did he think they were "War Drobe" and "Spare Oom"? He mispronounces them like the words are foreign to him.

~Riella

It's easy for us because we know exactly where Lucy came from. Tumnus is having a very surreal experience: Meeting a mythical creature as he is walking through the forest. Understandably, he assumes this creature came from some other country (perhaps the wild woods of the west). It is perfectly understandable that he thought she was telling him the of the country she came from.

Thing is, if he knows what a wardrobe and spare room are, why did he think they were "War Drobe" and "Spare Oom"? He mispronounces them like the words are foreign to him.

He simply misheard. He was fully expecting Lucy to say the name of the country she came from, and that was what he heard.

Funny story: I used to work at a bookstore. One day, a costumer walked in and said one of my co-workers "I would like to order this book ten seconds after you die." Awkward silence. Then the customer laughed and explained the title of the book was, in fact, "Ten Seconds After You Die." You all might conclude that the concept of books with titles was foreign to my co-worker, but I think that highly unlikely.

You're all overcomplicating something very simple.

Could it be that Lucy herself slightly mispronounced them? Or, (not that an English accent is mispronouncing, in fact, I think it is more accurate) if Mr. Tumnus was unused to English accents would that have fooled his ear?
My guess is that he was indeed shocked to find a (for him) otherworldly creature standing there, and also, I could picture Lucy having a slight and charming tendency to mispronounce things like many little girls do.
Also, could it be that they had wardrobes and spare rooms in Narnia but called them by different things? Such as "armoires" and "spare chambers", etc?

Could it be that Lucy herself slightly mispronounced them? Or, (not that an English accent is mispronouncing, in fact, I think it is more accurate) if Mr. Tumnus was unused to English accents would that have fooled his ear?
My guess is that he was indeed shocked to find a (for him) otherworldly creature standing there, and also, I could picture Lucy having a slight and charming tendency to mispronounce things like many little girls do.

If that's what C.S. Lewis was intending to convey, he didn't put anything in the book that indicated it. And if he really wanted to give that impression, I would think he might have been a bit more clear.

Also, could it be that they had wardrobes and spare rooms in Narnia but called them by different things? Such as "armoires" and "spare chambers", etc?

Now this is a great point. I wonder why no one has thought of this before. I'm sure they probably did call them something else. Narnia has a very medieval feel to it, and something like "spare chamber" fits in a lot better with that atmosphere than "spare room" does, IMO.

Is there anywhere in the CoN where a Narnian actually uses the terms "wardrobe" or "spare room"? If not, we might have our answer.

~Riella

I think that C.S.Lewis was playing around with this particular extract in the book, and on several levels. Yes, I agree that wardrobes are called different things in different places in the English speaking world. Same with Spare Rooms, I'd expect. And it is precisely why these items are so familiar and everyday that they get different names in different places. Down here a wardrobe could be called a Tall boy, a low boy, a closet, or a built-in. The dressing table could be a duchess, a dresser, a bureau or just a chest of drawers with a mirror attached. Apparently, C.S.Lewis and wardrobes go back a long way to when he and his brother, as children, hid in one to invent new worlds.

And yes, a none-too-bright faun who really should have paid more attention at school, would have had a shock at hearing the words in such an unfamiliar context. Tumnus only saw his own particular world, much like the hobbits in Tolkien's Shire. And to be fair to him, in a virtually one room cave, where would he have such a thing as a spare room, anyway?

And what was Mr Tumnus, a barely clad non-human, who was in Narnia to dance, sing and revel, doing at school, anyway? Or was this C.S.Lewis' rather wry poke at the level of exam bloopers that tend to go around colleges, even those of higher learning, from time to time? Did you know that the chief export from Turkey is Turkish delight? (My own schooldays blooper-by the way, I still don't know what it is, and I never lived it down) Or that a myth is a female moth? Or that Queen Victoria rained for 60 years?

To tell the truth I didn't notice this discrepancy between film and novel. I was too busy examining the books on Mr Tumnus' bookshelf. Is man really a myth?

I agree with glumPuddle, and Tumnus probably did not know what to expect. It never occurred to me that Tumnus might not be bright because he did not understand where Lucy, this "mythical creature" came from. I don't think it has any reflection on his intelligence or understanding at all and it is honestly not a big deal in any way.

Exactly. Tumnus has just discovered an amazing creature that he probably thought existed only in myth. Then he asks the creature where it came from, the last thing he expects to hear is "wardrobe" and "spare oom." I'm sure Tumnus knows exactly what those things are. He just assumed they were also the names of her county and city.

I completely agree with glumPuddle!
And I wouldn't be surprised if Lucy's accent sounded funny to Mr. Tumnus as well.

I think somethings may have just been written and don't really need an explanation or reason. In my opinion this is one of them.
But it's still fun to discuss.