Hi liverpool lass,
I believe the "ethnic origin" question on the census of that period simply refers to the closest non-Canadian nationality, it may not necessarily refer to the previous generation. And it always traced through the male line. So, for example, a person born in Canada whose father was born in England (mother born anywhere) would have "English" has their origin. Likewise, if the father had been born in Canada, but HIS father was born in England, the original person in question would still be classed as having english origins. (It is only in the last 10 years or so that "Canadian" has been an option for ethnic origin on the census

- the first year that was on the census the cultural distribution of the population changed dramtically...)
So, the short answer is that it tells you where the male line was originally from, but does not help to establish when they came over.
MJP