What is the earliest name ascribed to the book of Revelation? I was teaching Catechism last night, going over 'Revelation'.  I asked, "what's revelation?" and one girl answered, "It's the last book in the Bible". and I was like, "um yeah..." Well I wanted to say, it's also the entire Bible and I was kind of stumbling over my words there.

What I was wondering was, what was the Revelation/Apocalypse of John originally called? 

Eusebius called it the 'so-called Apocalypse of John', but if it was 'so-called' then what else might have it been called and when did it begin to go by the name 'Revelation'?
In many languages, the book is called "Apocalypse", which is Greek for "Revelation". It seems that the modern English convention is to use a translated, rather than transliterated, title. 
I am not aware of any title other than "Apocalypse", or a translation of "Apocalypse", for this book, in any language.

In the early English translations, there is some dissent about what to call it.


Wycliffe's Bible (1382-1395) used "Apocalips"
Tyndale's Bible (1525) used "Revelation"
Coverdale's (1535) called it "The apocalips or revelacion of S. John"
Douay-Rheims (1582) uses just "Apocalypse".


The King James (1611) called it "The Revelation of S. John the Divine" and, as the legally authorized English version, its usage seems to have stuck.

I checked the Koine text of Eusebius - he says "τῇ Ἰωάννου λεγομένῃ Ἀποκαλύψει", the relevant word being that middle "legomene". This often means just "called", without a negative slant, as in Luke 22:1 "the Festival of Unleavened Bread, which is called (legomene) Passover", or Matthew 2:23 "in a city called (legomenen) Nazareth". So I am not convinced that Eusebius is doing anything other than giving the name by which the book is known.

Later in the book (7.25) he says:


  Some before us have set aside and rejected the book altogether, criticising it chapter by chapter, and pronouncing it without sense or argument, and maintaining that the title is fraudulent. For they say that it is not the work of John, nor is it a revelation, because it is covered thickly and densely by a veil of obscurity. [...]  But I could not venture to reject the book, as many brethren hold it in high esteem. But I suppose that it is beyond my comprehension, and that there is a certain concealed and more wonderful meaning in every part. For if I do not understand I suspect that a deeper sense lies beneath the words.


He does not mention what these others call the book instead, though he does say they attribute it to the heretic Cerinthus. He says that the John who wrote this book was not the same John who wrote the gospel, but he is happy to say on the basis of the text that some John wrote it.