From the French "bougie" for candle. A long, thin, metal rod that is inserted into the urethra of the penis for sexual stimulation of the prostate.
(as is confirmed by the dictionary definition from Merriam-Webster)
"Are you guys talking about using a bougie? Well, when I was at Williams, we used to call 'em bouzshers!"
"I wandered into the sex shop, and there, this woman set me aside to explain to me how to use a bougie
. And then I turned around and noticed my mom, who had been staring at me the whole time."