There was the song “Bosom Buddies” from the 60’s musical “Mame” and the 80’s TV show “Bosom Buddies” with Tom Hanks and Peter Scolari playing men who cross-dress to successfully rent a room in an all-female building, but the phrase bosom buddies goes farther back than that!
It’s an updated American version of “bosom friend” or “bosom pal.” The phrase “bosom buddy” has become more widely used because of the alliteration. The term buddy is an Americanism.
In the book Anne of Green Gables written by Lucy Maud Montgomery and published in 1908, Anne refers to her friend, Diana Barry as her bosom friend.
In the book A Dictionary Of Biography by Richard Alfred (R.A.) Davenport published in 1832, the term bosom friend is used no fewer than 5 times in such passages as:
Peter Artedi, a Swedish physician and naturalist, born in 1705, was drowned at Amsterdam in his thirtieth year. He was the fellow student and bosom friend of Linnaeus, who, in honour of him, gave the name of Artedia, to one class of umbelliferous plants. His only work is the Ichthyologia, or History of Fishes, which was published by Linnaeus, after the author’s death.
The poet Michael Drayton (1563-1631) alluded to his student and English pastoral poet, William Browne (1591-1643) in a poem published in 1615 where he wrote:
Then the two Beaumonts and my Browne arose,
My dear companions whom I freely chose
My bosom friends; and in their several way
Rightly born poets.
The phrase bosom friends is used with such ease in this poem as to imply that the phrase was already used in every day English of the Elizabethan era.
Before its use in literary circles, the British had a saying that went like this: “A bosom friend afar brings a distant land near.” This saying was a direct translation of the Chinese phrase “Hǎi nèi cún zhī jǐ tiān yá ruò bǐ l.”
Historically Speaking 