The term case comes from the printing trade when the use of

moving type was invented in the early Middle Ages (Caxton or

Gutenberg?) and the letters for each font were stored in a

box with two sections (or "cases"), the upper case was for the

capital letters and the lower case was for the small letters.

The Oxford Universal Dictionary of Historical Principles (Feb

1993, reprinted 1952) indicates that this usage of "case" (as

the box or frame used by a compositor in the printing trade)

was first used in 1588.