Until the time of the invention of printing, the way letters were formed changed with fashion. When the printing press came in, the script of the time was Humanist, a style which went back to the old Caroline style as people had got tired of the almost illegible spiky gothic. Small letters ( miniscules) were derived from Humanist, and capitals were derived from Roman carved stone inscriptions. When pages of type were broken up into separate letters to wait to be reset as new pages, small letters of print were kept in the lower box, and capitals were kept in the upper box.hence lower case and upper case.