Question

Why were these groups called monasteries and how did they choose their members

Answer 1

Monasteries were based on groups of men who are monks and who centers their lives on religion.One becomes a monk generally through their neighborhoods for material support

Answer 2

The name probably originates from the name for the members, monks, who were male members of strict religious orders. Generally, one became a monk though one's family making arrangements, and often fathers would volunteer their children from a young age. Young women were also registered as nuns in abbeys, the equivalent of a monastery for a woman.