Because the teachers in the early universities were all Christian missionaries, they wore the black robes and headscarves in the monastery, and later gradually became the bachelor's clothes for college graduates.
The origin of bachelor's clothes should start with the development of Christianity in the middle ages. After the disappearance of the Roman Empire, education was no longer valued. The prosperity of Christianity led to the lack of clergy, and no one managed the parish.
Most of the parishes are located in schools. The church uses the parish as a place to impart basic knowledge education to priests and monks. These teachers who impart knowledge are called doctors or masters.
Later, teachers in some early universities were missionaries who taught knowledge before, wearing black robes and headscarves in monasteries. Later, they gradually evolved into bachelor's clothes in universities.