Monastic Sign Language

Monastic sign languages have been used in Europe from at least the tenth century by Christian monks, and some, such as Cistercian and Trappist sign, are still in use today—not only in Europe, but also in China, Japan, and the United States. Unlike deaf sign languages, they are better understood as forms of symbolic gestural communication rather than languages, and some writers have preferred to describe them as sign lexicons.

From Wikipedia · Monastic sign languages · CC BY-SA 4.0