The Confidential Agent - An Entertainment, by Graham Greene, 1939
The Viking Press, New York, 1967
Entrenationo is mentioned throughout the book, so I'll quote only a few choice passages here...
The Entrenationo Language Centre was on the third floor of a building on the south side of Oxford Street; over a bead shop, an insurance company, and the offices of a magazine called Mental Health. An old lift jerked him up; he was uncertain of what he would find at the top. He pushed open a door marked "Inquiries" and found a large draughty room with several armchairs, two filing cabinets, and a counter at which a middle-aged woman sat knitting. He said: "My name is D. I have come for a specimen lesson."
He said something which sounded like "Me tray joyass."... "The first words of the Entrenationo Language must always be ones of welcome."... "All this hate," Dr. Bellows said, "these wars we read about in the newspapers, they are all due to misunderstanding. If we all spoke the same language..." He suddenly gave a little wretched sigh which wasn't histrionic. He said: "It has always been my dream to help." The rash unfortunate man had tried to bring his dream to life, and he knew that it wasn't good - the little leather chairs and the draughty waiting-room and the woman in a jumper knitting. He had dreamt of universal peace - and he had two floors on the south side of Oxford Street.
Mr. K. said: "Tablo," and rapped on the table. He sat down with emphasis on one of the two chairs, and said: "Essehgo."
And here are a few samples of Intrenationo...
Actually... that's pretty much all there is to Entrenationo.
One thing I really liked about this book— the bits about the Entrenationo office. Sounds like a really quiet comfortable peaceful musty place with lots of wooden furnishings and reddish afternoon sunlight leaking through old lacy curtains that were hanging there when the Language Centre moved in and will still be hanging there when the Centre moves out...