The first mention of the Terebinth is by Benedictus Canonicus Sancti Petri (c. 1144), which names it "obeliscus Neronis", and by the "Mirabilia Urbis Romae" (a 12th-century guide of the city), where it is described like a circular monument composed with two superimposed cylinders (like Castel Sant'Angelo) lined with marble slabs and it is called "Tiburtinum Neronis"; the name "Tiburtinum" derives from the material of its revetment, the travertine ("lapis tiburtinus", that is from the city of Tivoli in Latin), while the name "Neronis" ("of Nero" in Latin) is typical of many toponyms and names of monuments of the Vatican area (like "prata Neronis", "pons Neronis", etc.