Case in point
Q From Chris Thalgott: Do you know the origin of the term case in point or case and point?
A It’s usually case in point, whose modern meaning is of some instance or example that illustrates what is being discussed:
Exports are growing faster than UK sales and nowhere more so than in the world's high growth economies. China is a case in point.
Derby Evening Telegraph, 10 Nov. 2010.
Though it is still very common, the phrase is a fossil, a fixed idiom. Within it is a much older idiom in point — now defunct — which meant something appropriate, relevant or pertinent. In point derives from the ancient Anglo-Norman French en point or en bon point, in which point could variously mean a condition, state, situation, or plight. A closely related surviving idiom is in point of fact.
This is an early example of the English in point:
Lord Fairfax was absent, and but a thin House. Query, what it means that the main question about transacting is so staved off? Some play or other is in point.
Diary, Thomas Burton, 25 Mar. 1659. He was a member of Parliament (here House) during the time of Oliver Cromwell. Play here is not a theatrical performance but a stratagem or scheme.
Case in point starts to be recorded during the late seventeenth century. Some early examples suggest that it began as a legal term in which case specifically referred to an action before the courts. This is an early instance:
The Case therefore before us seems to be what they call a Case in Point; the Relation between the Child and Father being what comes nearest to that between a Creature and its Creator.
The Spectator, Sep. 1711.