In typography, small letters, as opposed to uppercase—or capital—letters. The term is derived from the early days of printing, referring to the layout of the printer's typecase, which had the capital letters in the upper part (the "upper case") and the small letters in the lower part (or the "lower case"). Eventually, the California job case combined both the upper and lower cases into a single case (purportedly to enable traveling printers to better carry them on horseback during the California Gold Rush). Though no longer strictly appropriate, especially after the advent of the Linotype and phototypesetting, the terms upper- and lowercase have nevertheless stuck.
Much of the history of written communication involved only capital letters. Lowercase letters evolved in the Middle Ages as scribes tried to write faster and faster. Two handwriting styles—the formal hand of the church and the informal hand of the scholars—developed over the centuries. The Caroline miniscule (named after Charlemagne) is the direct ancestor of modern lowercase letters.
The evolution of alphabetic characters was spurred by three separate forces: Phoenician, Greek, and Roman. Until the invention of printing, there was little in the way of standardized forms of writing. In the Middle Ages, as scribes tried to write faster to keep up with the increasing demand for written material, short cuts were made so as to make serifs and terminal strokes with more fluid motions of the pen. Hence, the development of cursive writing. It primarily produced speed, but a welcome by-product was the beauty, symmetry, and simplicity of cursive writing. At this point, the uncial (from the Latin word uncus meaning "crooked") was still capital letter—or a majuscule—that rounded the straight lines. Hurriedly-written Roman capital letters were called Rustica. The uncial eventually mutated into the half-uncial, which was the dominant manuscript style by the eighth century. Charlemagne commissioned the Caroline alphabet—a true small-letter alphabet—from a monk named Alcuin. The Caroline miniscule eventually evolved into the gothic—or black letter—hand, the style of writing that Gutenberg sought to emulate with the first metal type and which became a prevalent type style during the nascent days of printing.
As might be expected, there were many regional and national differences in lettering styles, but it was Charlemagne who decreed that the Caroline miniscule was to be the dominant form of lettering used throughout his kingdom. The variations in metal type design that became widespread after the advent of printing were resurrections of characteristics of national handwriting styles.
As for the number of letters themselves, it was only in 1585 that the "v" and "j" began to be used as consonants and that "u" and "i" began to be used as vowels, thanks to Louis Elzevir. Even then, this didn't become universally accepted until 1822. Typecases therefore did not have allotted spaces for the "j" and the "u.