The twelfth month of the Zoroastrian calendar called esfend in Persian is a particularly auspicious month in the religious Zoroastrian calendar. Persian esfend comes from the Avestan speñtá, “auspicious, splendid, holy, bright.”
Avestan speñtá is related to Lithuanian šventas, Proto-Baltic-Slavic swęntŭs, Old Prussian swentas.
The Ancient Commentaries translate Speñtá as fzünik. Middle Persian fzünik comes from Avestan fshü “prosperous, of good fortune, flourishing.”
The epithet speñtá is applied to speñtá mainyü “the splendid mind energy/force, the sacred power/passion of the spirit.” Speñtá Mainyü is the sacred passion, spirit, mind-power of mazdá and his ahûrás.
The epithet speñtá also comes in connection with speñtá ár-maiti “the auspicious melody/flow of a rightly and harmoniously ordered mind and spirit.”
The 12 month is speñtá “auspicious, sacred,” because it is a month dedicated to the Auspicious Immortals, a month for finding the sacred within, a month for self discovery and lighting the sacred flames.
Rue called esfand in Persian is a sacred plant, a most holy herb in Zoroastrianism, with roots going back to our sacred Indo European past.