Tartarus — A Greek word, not found in the Hebrew, used by Peter in 2 Peter 2:4 when referring to the angels who were cast down to hell (Tartarus) at the time of Noah's flood. Used twice in the Septuagint, the Greek translation of the Old Testament. First time was when translating the word "field" or "plain" where the living creatures play (or mock) in Job 40:20 in a reference to Behemoth (great land animals, possibly ancient dinosaurs).

Second time was when translating the word "deep" in Job 41:31-34. In normal usage e.g. Gen 1:2 Abyssou in Greek, Tehowm in Hebrew

Leviathan
In verse 32 in a reference to Leviathan. "He makes the depths to boil like a pot, he makes the sea like a pot of ointment. He makes a path to shine after him, one would think the deep to be hoary (grey-haired). Upon earth there is not his like, one made without fear. He beholds every high thing, he is king over all the children of pride ('strutting as lions')."

With regard to "Leviathan" in modern Hebrew, it is their word for "Whale", and quite possibly the origin of those Latin and Norse words "Wailing" and "Woe", see Job 3:8 where KJV translates it as "Mourning". Spoken of in judgment in Isaiah 27:1 "In that day (of the Lord's return) the LORD with his severe, great and strong sword shall attend to (shall punish) Leviathan the piercing (literally "fleeing") serpent, even Leviathan that crooked (bent) serpent, and he shall slay the Tannin (i.e. the Dragon) that is in the sea", the embodiment of Satan, see John's words Revelation 12:9 , also Genesis 3:15 and Psalms 74:14

With regard to "Tannin", the Hebrew word for "Crocodile", it was translated in the Greek and Latin as "Cetus" i.e. "Whale" (Genesis 1:21, Matthew 12:40), as "Serpent(s)" (when Moses stood before Pharaoh and his magicians), but mostly as "Dragon".