How did literature contemporaneous to the New Testament understand the "Second Death"?

The term "second death" appears four times in Scripture, all in Revelation (all NKJV, emphasis added): > He who has an ear, let him hear what the Spirit says to the churches. He who overcomes shall not be hurt by **the second death**. (Rev. 2:11) > Blessed and holy is he who has part in the first resurrection. Over such **the second death** has no power, but they shall be priests of God and of Christ, and shall reign with Him a thousand years. (Rev. 20:6) > Then Death and Hades were cast into the lake of fire. This is **the second death**. (Rev. 20:14) > But the cowardly, unbelieving, abominable, murderers, sexually immoral, sorcerers, idolaters, and all liars shall have their part in the lake which burns with fire and brimstone, which is **the second death**. (Rev. 21:8) In 20:14 and 21:8, we're told the lake of fire "is" the second death. Scripture often will say an image "is" something else to let you know what the image really means. For example, when Joseph interpreted Pharaoh's dream, he says the seven good cows and seven good heads of grain "are" really seven years of food, while the seven thin cows and seven scorched heads of grain "are" really seven years of famine (Gen. 41:26). Jesus uses similar "is" language to explain what the elements of His parables really meant (e.g., Luke 8:11-15). With Revelation being a book of symbols, I'd like to know what the "second death" is, as it appears to be an interpretation of the lake of fire. If I take "second death" literally, I'd understand it as literally dying a second time. Is that how the Jewish literature used the phrase during and before the first century? What documents during and before the first century use the expression "second death," and what did it mean? Did it reference (1) eternal torment; (2) permanent, literal death/annihilation; (3) temporary, corrective punishment; or (4) something else? (I'm asking specifically for extra-biblical sources during and before the first century, not sources after.)