relating to small (not capitalized) letters that were kept in the lower half of a compositor's type case
Lowercase letters; a and b and c etc.
source: WordNet 3.0
Pertaining to, or kept in, the lower case; -- used to denote the small letters, in distinction from capitals and small capitals. See the Note under 1st Case, n., 3.
source: Webster 1913
noun
the characters that were once kept in bottom half of a compositor's type case