It is hard to believe that there is a connection between the slang term for female breasts and the Black Death, the deadly bubonic plague pandemic that afflicted Europe between 1348 and 1350, killing 30% to 60% of Europe’s population.
(Pictured above is an illustration of the Black Death from the Toggenburg Bible, 1411. The buboes characteristic of the bubonic plague are quite evident).
This is the history of the use of the word “boobs”, meaning breasts, as presented in Cassell's Dictionary of Slang:
Bubo and Boobo (plural Bubos and Boobos) - from the 14th century, refers to a swelling of some kind. Swelling of the lymph nodes was a common symptom of the plague, with the result that swelling of the chest came to be referred to as “boobos”. The word bubonic is derived from bubo.
Bubby - from the late 17th century, refers to a breast or both breasts together.
Bube - from the late 18th century, refers to a venereal disease. Bube also is a derivative of bubo.
Booby - started around the 1910s. It has been established that it came from Bubby.
Boob - started in the 1940s, and traced to the word booby.
There is an alternative theory that it comes from the German word “bubbi”, meaning “teat”, as in Thomas D’Urfey’s 1690 New Poems:
“The Ladies here may without Scandal shew Face
or white Bubbies, to each ogling Beau.”
The word booby for a stupid person, later shortened to boob, as well as the word booboo for a blunder or mistake, probably derive from the Spanish bobo, meaning a foolish or stupid person as well as being the name of a type of bird which was slow, stupid, and easy to kill.