From the longer Wikipedia page 
Tironian notes (notae Tironianae) is a system of shorthand said to have been invented by Cicero's (Wikipedia page _scribe Marcus Tullius Tiro (Wikipedia page . Tiro's system consisted of about 4,000 signs, somewhat extended in classical times to 5,000 signs. In the European Medieval period, Tironian notes were taught in monasteries and the system was extended to about 13,000 signs (see scribal abbreviations). The use of Tironian notes declined after 1100 but some use can still be seen through the 17th century.