I have used notebooks in the 1960s till 1980s with the format 9" x 7" (229 mm x 178 mm); this was common in Europe (I have bought them at least in Switzerland, France, England). Now I cannot find any reference to this format and not find a name for it. What was it called?
According to Wikipedia 7" x 9" seems to be a traditional British paper size from before the ISO standard and it's called Imperial.
According to the British Association of Paper Historians (BAPH), 7" x 9" was called Small Post Quarto. Two completely different sizes are given for "Imperial" depending on whether it was cartridge paper, or book/drawing paper.