the bosom: the front of the chest and the enclosing arms (reaching down to the lap), where a person holds someone or something close, and the fold of the outer robe there used as a pocket
This is a body word before it is anything else. It names the warm hollow at the front of a person, the chest and the circle of the arms, the natural place to gather a child, a lamb, or a loved one and hold them safe against yourself. From that one concrete picture the whole range of the word unfolds.
Held close in this space, a person is cherished, so the word carries the warmth of family and marriage: a nursing father carries the people in his bosom, a poor man's pet lamb sleeps in his, and a cherished spouse is called the wife, or the husband, of one's bosom. The same fold at the chest, formed by the loose outer robe belted at the waist, doubles as a pocket. People kept coins, cast lots, and slipped bribes into it, and Scripture pictures God repaying a person by pouring the reward, good or bad, straight into that fold.
Because it is the innermost place a person keeps things close, the word also turns figurative: anger settles in the bosom of a fool, an unanswered prayer comes back into one's own bosom, and a man carries insult in his bosom the way he would carry a burden pressed to his chest.