Prime describes what’s first in excellence, rank, or degree. The prime minister is the highest-ranking official. The prime interest rate is a bank’s best rate. In math, a prime number is not divisible, except by one and by itself. But the earliest sense was time. The Romans called sunrise prima hora. Early Christians called the second canonical hour Prime, which was traditionally said during the early morning. Its religious origin is still present the noun primer, which was a layperson’s prayer book.
Image courtesy of Catholic Spiritual Direction