Early 17th century; earliest use found in John Healey (c1585–c1616), translator. Either from the name of Pythagoras + -ism, perhaps after Platonism, or directly from Hellenistic Greek Πυθαγορισμός principles and practice of Pythagoras from ancient Greek Πυθαγόρας, the name of Pythagoras + -ισμός, after Πυθαγορίζειν. Compare French Pythagorisme.