Nicholas's reference is the Medieval Monk

Monks in a medieval monastery were expected to live simply with few possessions, attend services at all hours of the day and night, and perhaps even take a vow of silence. Still, monks could at least benefit from a secure roof over their heads. Another plus was a regular food supply which was of a much higher standard than the vast majority of the medieval population had access to. To symbolize the giving of their lives to God, monks were to mimic Saint Paul’s hair. Saint Paul was said to be a bald man; which meant that every monk was to shave their head clean. Saint Paul was revered by many Catholic Christians for writing thirteen books of the Bible and spreading Christianity across the Roman Empire in his lifetime. One of the problems with doing so was that the bible forbids cutting the hair at the edge of one’s head or beard. This presented a dilemma for many monks who wanted to mimic Saint Paul but were afraid to go against the bible.

A solution to this dilemma was a haircut that satisfied both the bible and the pope. Monks shaved the top of their heads to show tribute to Saint Paul and kept the edges of their hair to also respect the bible. The new bizarre haircut was named the tonsure and was worn by almost every Catholic monks in Europe in medieval times.