[CSS2] Technical term 'canvas origin' not defined

[yroc]

The term canvas origin, used in 10.1 Definition of "containing block"

The containing block in which the root element lives is a rectangle called the initial containing block. For continuous media, it has the dimensions of the viewport and is anchored at the canvas origin; it is the page area for paged media. The 'direction' property of the initial containing block is the same as for the root element.

and in E.2 Painting order

The canvas is transparent if contained within another, and given a UA-defined color if it is not. It is infinite in extent and contains the root element. Initially, the viewport is anchored with its top left corner at the canvas origin.

doesn't appear to be defined anywhere in the spec.

[fantasai]

That statement is wrong anyway, on rtl pages it's the top right...