are youn Taking the piss? Derived from the build-up of urine in the bladder puts pressure on the man's prostate gland, resulting in an erection. In the 17th and 18th Centuries, a man who was thought to be unnecessarily arrogant would be described as 'piss-proud'. If you were to ridicule someone for being too 'full of themself', you would 'take the piss' out of them.