Why is the ninth month called September?
1530, "goat sent into the wilderness on the Day of Atonement, symbolic bearer of the sins of the people," coined by Tyndale from scape (n.) + goat to translate Latin caper emissarius, itself a translation in Vulgate of Hebrew 'azazel (Lev. xvi:8,10,26), which was read as 'ez ozel "goat that departs," but which others hold to be the proper name of a devil or demon in Jewish mythology (sometimes identified with Canaanite deity Aziz).
Jerome's reading also was followed by Martin Luther (der ledige Bock), Symmachus (tragos aperkhomenos), and others (cf. French bouc émissaire), but the question of who, or what (or even where) is meant by 'azazel is a vexed one. The Revised Version (1884) simply restores Azazel. But the old translation has its modern defenders:
Azazel is an active participle or participial noun, derived ultimately from azal (connected with the Arabic word azala, and meaning removed), but immediately from the reduplicate form of that verb, azazal. The reduplication of the consonants of the root in Hebrew and Arabic gives the force of repetition, so that while azal means removed, azalzal means removed by a repetition of acts. Azalzel or azazel, therefore, means one who removes by a series of acts. ... The interpretation is founded on sound etymological grounds, it suits the context wherever the word occurs, it is consistent with the remaining ceremonial of the Day of Atonement, and it accords with the otherwise known religious beliefs and symbolical practices of the Israelites. [Rev. F. Meyrick, "Leviticus," London, 1882]Meaning "one who is blamed or punished for the mistakes or sins of others" first recorded 1824; the verb is attested from 1943. Related: Scapegoated; scapegoating. For the formation, cf. scapegrace, also scape-gallows "one who deserves hanging."
Lev. 16:8-26; R.V., "the goat for Azazel" (q.v.), the name given to the goat which was taken away into the wilderness on the day of Atonement (16:20-22). The priest made atonement over the scapegoat, laying Israel's guilt upon it, and then sent it away, the goat bearing "upon him all their iniquities unto a land not inhabited." At a later period an evasion or modification of the law of Moses was introduced by the Jews. "The goat was conducted to a mountain named Tzuk, situated at a distance of ten Sabbath days' journey, or about six and a half English miles, from Jerusalem. At this place the Judean desert was supposed to commence; and the man in whose charge the goat was sent out, while setting him free, was instructed to push the unhappy beast down the slope of the mountain side, which was so steep as to insure the death of the goat, whose bones were broken by the fall. The reason of this barbarous custom was that on one occasion the scapegoat returned to Jerusalem after being set free, which was considered such an evil omen that its recurrence was prevented for the future by the death of the goat" (Twenty-one Years' Work in the Holy Land). This mountain is now called el-Muntar.