Etymologiae, Book I, chapters 22-24: De notis vulgaribus to De notis militaribus
Chapter XXII. On common shorthand marks Ennius first invented the common marks, eleven hundred in number. The use of the marks was that, whatever was said in debate or in the courts, several scribes standing by at once, the parts being divided among them, should write down how many words each took and in what order. At Rome the first to devise marks was Tullius Tiro, the freedman of Cicero, but only of prepositions. After him Vipsanius, Philargius and Aquila, the freedman of Maecenas, each added others. Then Seneca, having gathered all together, arranged them and increased the number, and made a work of five thousand. The marks are called notae because they note (notent) words or syllables by characters set before them and recall them to the knowledge of readers; those who have learned them are now properly called notaries.
Chapter XXIII. On legal marks Certain letters in the books of law are marks of their words, that writing may be quick and shorter. For example, bonum factum was written with B and F, senatus consultum with S and C, respublica with R and P, populus Romanus with P and R, dumtaxat with D and T, mulier with the letter W turned on its back, pupillus with P, pupilla with a reversed C, caput with a single K, calumniae causa with two K’s joined, iudex esto with I and E, dolus malus with D and M. Of this kind we find very many like marks in ancient books. These marks of the law the recent emperors decreed should be abolished from the codes of laws, because through them clever wits deceived many who did not know them, and so they ordered that letters be written in the laws in such a way as to bring no errors, no ambiguities, but to show openly what is to be followed and what avoided.
Chapter XXIV. On military marks In the little rolls also, in which the names of soldiers were contained, there was among the ancients a proper mark, by which it was seen how many of the soldiers survived and how many had fallen in war. The Tau, a mark set at the head of the line, designated a survivor; the Theta was placed at the name of each one deceased. Hence it also has a dart through the middle, that is, the sign of death. Of this Persius says: “And he is able to prefix the black theta to the fault.” When they wished to signify inexperience, they used the letter Lambda, just as they signified death when they put Theta at the head. In the distribution of pay also there were proper marks.