It's a term from web designers - it's called 'reset' because by including it you were 'resetting' the styles that were different between different browsers to a common set of stylings, however it's come to be a basic template that designers then elaborate on.
Google came up with this as a history primer which looks close to right:
I don't know think there's an equivalent for ePub rendering space, because as the OP is starting to realize, nobody's really considered this. Likely because the various renderers (even those using the same rendering engine) vary so widely in what they do, and we (the vendors) haven't published much information about what we are doing. As a for instance if you look at the same EPUB on a Nook Color, a Sony T1, and in ADE 1.8 - you will find all three different renderings:
1.) Unless the font is embedded - the font used will be different (and even then it may be overridden on the NC)
2.) EInk vs Color makes a big difference, that the browser reset CSS authors haven't thought about.
2.) Linespacing,font size, margin and other override settings are available on the T1 and NC, but not in ADE (well font size is).