Ye gads but you folks are all *young!
Mae West was an actress, playwriter and movie star amply endowed with a formidable bosom.
She was born in the late 1890s and was in the public eye for many years. Probably one of the earliest "Blonde Bombshells" and "sex symbol."
However, in the early years of WWII for some reason that now escapes me, Mae West had a chest Xray and the Xray was published in LIFE magazine ... Naturally the breasts' shadows were readily visible. Anyways, after the photo was published the American servicemen started calling their life vests Mae Wests. The expression spread like wildfire!
Now, checking OED it says a Mae West is an inflatabale life jacket originally issued to the Royal Air Force in 1939-1945.
That's all I got or could recall, folks.