“A country mile”
What it means
A long and imprecise distance.
Where it comes from
Before the statute mile was enforced consistently, rural distances were customary. A mile between two villages was however far it had always been, and the figure owed more to habit than to measurement.
How sure are we?
Plausible and consistent with the evidence, though the phrase itself is comparatively modern. The underlying fact is solid: England, Scotland and Ireland all had competing miles, and local usage was slower to change than legislation.