The first mention of this word and subject in Scripture, is in Leviticus 4:22, and relates to a "ruler". Dr. Bullinger comments on this verse that the Hebrew word used refers to "Kings", (1Kings 11:34, Ezek. 34:24 & 46:2), to the head of a tribe (Num. 1:16- 46 & 34:18); and to one whom God has appointed!
The common usage of the term is probably derived from the account given in Lev. 16:21-22. However, according to Wikipedia such practice had been common in several of the Codes of the Mideast in the past, see: extracts below from Wikipedia:
Scapegoat derives from the common English translation of the Hebrew term azazel which occurs in Leviticus 16:8 after the prefix la. The lexicographer Gesenius and Brown - Driver - Briggs Hebrew Lexicon give la-azazel as a reduplicative intensive of the stem azel "remove", hence la-azazel, "for entire removal". This reading is supported by the Jewish Greek Bible translation as "the sender away (of sins)". Later Jewish sources in the Talmud (Yoma 6:4,67b) give the etymology of azazel as a compound of "az", strong or rough, and "el", mighty, that the goat was sent from the most rugged or strongest of mountains.
"And Aaron shall cast lots over the two goats, one lot for the Lord and the other lot for Azazel."
Alternatively, broadly contemporary with the Septuagint, the pseudepigrapical Book of Enoch may preserve Azazel as the name of a fallen angel and from the Targumsonwards the term azazel was also seen by some rabbinical commentators as the name of a Hebrew demon, fallen angel, or pagan deity. The two readings are still disputed today.
English Bible versions traditionally follow the translation of the Septuagint and Latin Vulgate which interpret azazel as "the goat that departs" (Greek tragosapopompaios, "goat sent out", Latin caper emissarius, "emissary goat"). William Tyndale rendered the Latin as "(e)scape goat" in his 1530 Bible. This translation was followed by following versions up to the King James Version of the Bible in 1611: "And Aaron shall cast lots upon the two goats; one lot for the Lord, and the other lot for the scapegoat." Several modern versions however either follow the reading as a demon, Azazel, or footnote "for Azazel." as an alternative reading.
A concept superficially similar to the biblical scapegoat is attested in two ritual texts in archives at Ebla of the 24th century BC. They were connected with ritual purification on the occasion of the king's wedding. In them, a she-goat with a silver bracelet hung from her neck was driven forth into the wasteland of "Alini"; "we" in the report of the ritual involves the whole community. Such "elimination rites", in which an animal, without confession of sins, is the vehicle of evils (not sins) that are chased from the community are widely attested in the Ancient Near East.
The Ancient Greeks practiced a scapegoating rite in which a cripple or beggar or criminal was cast out of the community, either in response to a natural disaster (such as a plague, famine or an invasion) or in response to a calendrical crisis (such as the end of the year). The scholia refer to the pharmakos being killed, but many scholars reject this, and argue that the earliest evidence (the fragments of the iambic satirist Hipponax) only show the pharmakos being stoned, beaten and driven from the community.
The scapegoat was a goat that was designated la-aza'zeyl; either "for absolute removal" (Brown-Driver-Briggs Lexicon) or possibly "for Azazel" (some modern versions taking the term as a name) and outcast in the desert as part of the ceremonies of the Day of Atonement, that began during the Exodus with the original Tabernacle and continued through the times of the temples in Jerusalem.
Throughout the year, the sins of the ancient Israelites were daily transferred to the regular sin offerings as outlined in the Torah in Leviticus Ch 16. Once a year, on the tenth day of the seventh month in the Jewish calendar, the Day of Atonement, the High Priest of Israel sacrificed a bull for a sin offering for his own sins. Subsequently he took two goats and presented them at the door of the tabernacle with a view to dealing with the corporate sins of God's people -- the nation of Israel. Two goats were chosen by lot: one to be "The Lord's Goat", which was offered as a blood sacrifice, and the other to be the "Azazel" scapegoat to be sent away into the wilderness. The blood of the slain goat was taken into the Holy of Holies behind the sacred veil and sprinkled on the mercy seat, the lid of the ark of the covenant. Later in the ceremonies of the day, the High Priest confessed the sins of the Israelites to Yahweh placing them figuratively on the head of the other goat, the Azazel scapegoat, who "took them away" never to be seen again. The sin of the nation was thus "atoned for" (covered) by the "The Lord's Goat" and "The Azazel Goat".
In Christian thought this process prefigures the sacrifice of Christ on the cross through which God has been propitiated and sins can be expiated. Jesus Christ is seen to have fulfilled both of the Biblical "types" - the Lord's goat that deals with the pollution of sin and the scapegoat that removes the "burden of sin". Christians (of the Roman teaching) believe that sinners who own their guilt and confess their sins, exercising faith and trust in the person and sacrifice of Jesus, are forgiven of their sins.
Since the second goat was sent away to perish, the word "scapegoat" has developed to indicate a person who is blamed and punished for the sins of others.
As can be seen from the above, there are differing opinions as to meanings, but the only one which is of importance and interest to sincere Bible students is what Almighty God (The Jehovah of the Jews) intended in His statements in Leviticus!
What is common to all understandings is that there is a 'transfer' of blame and guilt to an alternative object, in this case a Goat! What seems to be missed in the teaching on this subject, especially in the comments on the Biblical account in Lev. is the gender of the animal! The present lack of clarity, and emphasis on the second goat's representation, reduces the understanding of future Israel.
The statement is made in Lev. that the goats for the expiation of the Priest's sin is to be male, (confirmed in Lev. 4:23), and also for the scapegoat released into the wilderness! The KJV translation in Chp. 16:5 shows "two kids" which should be, "shaggy he-goats" corrected by Dr. Bullinger and Dr. Ginsburg, as he was using Dr. Ginsburg's notes on the Old Testament (OT), see: Preface to The Companion Bible page 9.
This gender differentiation is of critical importance to fully understand the depth of Jehovah's message to His people Israel, and to Christians in this Age, and has links to Genesis in the Garden of Eden. As in Genesis God's order of responsibility was on Adam's shoulders, so here also the males burden of responsibility is demonstrated in both the Priest and Israel's future!
In the points in demonstration in Lev. 16, Aaron had become careless as to his appearances before Jehovah (v2). His sons had only recently been killed for just such lack of rigid care and adherence to Jehovah's requirements of ritual; which were absolutely needed in the case of the Jews, due to the situation created by Satan in his rebellion against God, see: Satan's Motivation:
The critical element in Israel's appointment was that like Gentile peoples now, they had/have free-will; the very element that Satan had abused in his own past rebellion, and had successfully persuaded Eve, followed by Adam to use in their disobedience to God's commands. As is made clear, Israel used the free-will to go against Jehovah's teaching and wishes.
It was not God's wish that Aaron should die for his laxity, so He instigated the route to save him from death in his capacity of Priest (knowing Aaron's grief at the death of his sons, and the effect it was having on his performance, and His compassion for all humankind). This is tabulated in Lev. 4:22, "When a ruler has sinned"; which also denotes one whom God has appointed. In this ritual described in Lev. 4:22-26, this male goat is killed as "the sin offering" to God expiating the sin of the Priest, and restoring him to suitability for his Office. In this case Satan had attempted to thwart the future use of the Priesthood, in particular in the Kingdom Age; see: Ezekiel.
The second he-goat which had been selected by "Urim and Thummim" to be the scapegoat, was presented alive before Jehovah, prior to being released deep in the wilderness, Lev. 16:10. The Hebrew word for "for" in vs 8 and 10 is AZAZEL, which Dr. Ginsberg and Dr. Bullinger both conclude means "for Jehovah" (see: notes vs 8,10, and 22) which draws the conclusion that the scapegoat was not sent away in judgment or atonement, but in peace and liberty, as the first goat had cleared the iniquity by its death, but however, doomed to deep wilderness wanderings! This satisfied the "rules of engagement" between Jehovah and Satan, "and all righteousness" as stated by our Lord prior to His water Baptism during the Dispensation of John the Baptist, necessary during the Age of the Jew prior to Acts 28:28.
In the case of Aaron, he was the first to be appointed to Priesthood, and all the subsequent Priests were of his line, both Levites and Zadok, the latter having an elevated role in the Kingdom Age, Ezk. 43:19 and 44:15, due to their faithfulness!
In the case of the ordinary (common) people sinning, a female goat was used as the substitute sacrifice (Lev. 4:27-32 and 16:15), which gave a clear definition between Priesthood and people!
Both Aaron and Israel are 'appointed', and therefore are in the category described in Exodus 19:6, and confirmed in Revelation 1:6; "a Kingdom of Priests unto God, and a holy Nation". As such, and bearing in mind that the first usage of "scapegoat" was relevant only to them at that time, the first goat and second goat are embodied in Jesus the Christ, their Messiah in both roles, who is yet to return to rescue them from Satan, and whom they will see in detail as described in Zechariah 12, particularly 12:10!
The first goat was sacrificed for their collective sin, as the future Priestly Nation which they rejected in Christ Jesus; which rejection placed them in the "wilderness" which is representative of the scapegoat; from which they have not yet returned. When they do they will fulfil the prophecy of Jesus in Luke 15:11 regarding "the prodigal son". It has to be remembered that they are Jehovah's "first born son" (Ex. 4:22), (see: "Israel; My Firstborn son") the prodigal, in the wilderness! He who was sacrificed for them will return from His position at the right hand of Jehovah, who was "for Jehovah" (Azazel) in all He did on Earth; and He as Melchisedec, (see: Melchisedec and the Lamb of God ).