1743, from Zoroaster, from Latin Zoroastres, from Old Persian Zarathushtra, 6c. or 7c. B.C.E. Persian religious teacher. The name appears to be literally "whose camels are old," from *zarant "old" (cognate with Greek geron, genitive gerontos "old;" see gerontology) + ushtra "camel." As a noun from 1811.
-ism
word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.