"Octavo (usually abbreviated 8vo, 8°, 8o, or Oct.) is a book size resulting from the use of standard size sheets of paper folded three times to make eight leaves. Each leaf is usually printed on each side, so this creates a signature of 16 pages in total. It was introduced by Aldus Manutius of Venice, when he produced Virgil's Opera in the octavo format, in 1501, in order to facilitate portable reading for men of leisure."
If you don't know: just 8 issues of Octavo were produced by London-based design studio 8vo between 1986 and 92. All but the final issue were printed magazines of the finest quality (the last was a CD ROM produced at a time when such things were "cutting-edge") The contents often had a distinct leaning towards matters of modernist typography: Zwart, Schuitema, Burchatz et al, alongside more contemporary exponents and theorists.
To find out more about their awesome work buy the book! I did. well.. it was given to me..
Now disbanded the partners - Mark Holt, Hamish Muir and Simon Johnston - are working independantly and are still doing interesting things..