Bosom: κόλπον – kolpos

So it was that the beggar died, and was carried by the angels to Abraham’s bosom. The rich man also died and was buried.

(Luke 16:22) NKJV

The simple explanation for the phrase Abraham’s bosom is that Abraham was giving Lazarus a hug, however there’s precedent to use it to refer to a physical location.

It’s part of the meaning of the word translated as bosom. It can refer to a bay or gulf in a coastline, which is similar to the idea presented by a chamber in the lower mantle which overlooks the great gulf and hell below.

Bosom: κόλπον – kolpos

• the bosom
  1. sing. and plur: bosom;
     • (sinus) the overhanging fold of the garment used as a pocket,
     • properly, the upper part of the chest where a garment naturally folded to form a “pocket” – called the “bosom,”
     • the position synonymous with intimacy (union),
     • lap.
  2. a bay, gulf
     • a bay of the sea, gulf, creek.