Note 889 — Chapter II · THE ROMAN EMPIRE UNDER ANASTASIUS: THE INHERITANCE OF JUSTINIAN (continued 2)
Reading edition
Introduced, perhaps, by Boethius; De Arith., i, 1. Τετρακτὺς is found in Greek; Anna Comn.; i, pref.; see Ducange, sb. voc. The latter word is really the original and goes back to Pythagorean times.