Hades

His soul was not left in Hades..

Acts 2:31

Seeing the Greek pagan underworld being referred to in the New Testament is quite jarring until you remember that St Luke is writing in Greek. Is St Peter who is speaking here, using Greek, or has he been translated? I'm no scholar. He's a fisherman from Galilee, so hardly a scholar himself, but we know Greek is the lingua franca at this time, (as English often is today) so he may have known it fairly well. Plus the Holy Spirit is really good at languages, unlike me. 

The thing to avoid doing here is to assume Hades is a myth. It's true it has different associations from the Hebrew word Sheol, which is used by David in the Hebrew version of Psalm 16:10 that Peter refers to, but the world of the dead is clearly being referred to either way. The Greek Septuagint is the Greek OT, and hence the book St Peter may be quoting directly.. 🤔

The word my Japanese Bible uses, Yomi (黄泉) has different associations again..