Talk: HO scale
I saw something that said H0 is related to a scale the Germans introduced (may have been called "Zero" Scale).
It was something like 1:45. The British modified it to 7mm = 1 foot, giving a ratio of about 1:43.5, which if you halve that, it is 1:87, or half zero (H0).
The issue many had with O scale (1:48) is that the track gauge is wider than it should be, in proportion to the train that rides on the track. Many tinplate trains were wrong in terms of proportions, because of the need to run on O27 curves.