bosom buddy / friend

What is the origin of the idiom "bosom buddy" and when to use it?

Its origin can be traced back to the 16th century, where the word "bosom" referred to the chest area and was often associated with warmth, comfort, and affection. The phrase "bosom friend" was used in literature, particularly in Shakespeare's plays. The term gained popularity in the 20th century and is believed to have been coined in America. It became a commonly used phrase to describe a friendship that is so close, it feels like the two people are almost inseparable. Today, the term is still in use, and its meaning remains largely unchanged, referring to a close and trusted friend who is like family.