By definition, the ancient Greek word τῠ́ρᾰννος means absolute ruler or monarch However, in light of the New Testament events, Tyrannus is the name of prince, a Greek rhetorician, in whose “school” at Ephesus St.Paul the apostle carried out most of his ministry, disputing and reasoning daily over the course of two years concerning the Gospel with those who came to him (Acts 19:9).
D Syriac that St.Paul taught at the school “from the 5th hour unto the 10th”, meaning eleven o’clock in the morning until four in the afternoon. This likely to have been the case because these were the hottest hours of the day when most people rested after the midday meal. So the apostle Paul sought to take advantage and utilise these hours. During these times, the hall would normally be vacant, and perhaps rent cheaper, (Tyrannus would normally teach in the cooler morning hours). The halls or rooms of the philosophers were called σχολαί among the later Greeks (Liddell and Scott,s.v.).