 The term "Gnosticism" does not appear in ancient sources, and was first coined in the 17th century by Henry More in a commentary on the seven letters of the Book of Revelation, where More used the term "Gnosticisme" to describe the heresy in Thyatira.The term "Gnosticism" was derived from the use of the Greek adjective "gnostikos" (Greek γνωστικός, "learned", "intellectual") by St. Irenaeus (c. 185 AD) to describe the school of Valentinus as "he legomene gnostike haeresis" "the heresy called Learned (gnostic).