History
The story of Monastic Sign Language starts with Benedict of Nursia (480 CE), also known as Saint Benedict. He left his studies at a young age to pursue a life of spiritual refinement, and by the age of thirty-nine he had twelve monasteries to his name. This eventually lead him to write down all the rules and standards that reigned in his monasteries in the Rule of Saint Benedict (529CE).
In the sixth chapter Of Silence Saint Benedicts writes about the virtues of silence and the dangerous power of speech, and eventually this translated into the practice of silence in Benedictine monasteries. This did not mean absolute silence at all times, but still during most of the day in most areas of the monastery.
When exactly monks started using signs for the first time, we don't exactly know. But we do know where it started: the abbey of Cluny in France. Being far larger than its contemporaries, the monks there likely had an especially hard time going about their daily tasks without communicating.
Eventually the use of signs also spread throughout the rest of Europe, North America, and even Asia.
Monastic Sign Language