The second death is an eschatological concept, in Judaism and Christianity, related to punishment after a first, natural, death.
Although the term is not found in the Hebrew Bible, Sysling, in his study (1996) of Teḥiyyat ha-metim (Hebrew; "resurrection of the dead") in the Palestinian Targums, identifies a consistent usage of the term "second death" in texts of the Second Temple period and early Rabbinical writings. In most cases, the "second death" is identical with the judgment, following resurrection, in Gehinnom at the Last Day.
In Targum Neofiti (Neof.) and the fragments (FTP and FTV), the "second death" is the death that the wicked die.
Targum Isaiah has three occurrences. The first is 22:14 where the Aramaic paraphrases the Hebrew as "This sin will not be forgiven you until you die the second death." The final two examples are from Targum Isaiah 65 which sets the scene for an apocalyptic final battle. Targum Isaiah 65:6 paraphrases the Hebrew in line with the interpretation of the penultimate verse of the Hebrew Isaiah, found in the Gospel of Mark, where "their worms does not die" is equated with Gehinnom. Here both Targum Isaiah and Gospel of Mark supply the term "Gehinnom", where Hebrew Isaiah simply concludes with the heaps of corpses following the last battle where "their worms do not die", making no further eschatological extension into resurrection and judgment.
Tell me now tell me now
What is it you're afraid of
To be alive or to be dead
When you look in the mirror what do you see
Life is short like blood is red
Don't you know some day you will be gone
You got to change your evil ways
You run around like you live forever
What do I have to say
The casket is closing
See the lid come down upon you
Now hear the dirt falling on the wood
So how could you ever hold your breath
My friend your not dead
Until you second death
Hear the wolf now as he's calling
He wants you to join the pack
Every night it's the same old song and dance
Can't you tell that his wool is black
The red rose that he is giving you
Don't you know that it wilts away
Do you want to be dead forever
Don't kill your soul this way
The casket is closing
See the lid come down upon you
Now hear the dirt falling on the wood
So how could you ever hold your breath
Don't you know that the sun is soon to set on you
Is your name in the book of life
Or will you burn in the lake of fire and flames and death
Your second death