See a man about a horse

Recently I was at the doctor's office and the nurse practitioner was taking blood. I mentioned that the doctor mentioned he wanted to do a urinalysis. The n-p gave me a cup and said go into the bathroom and "letter following 'O' into a cup". I was quite shocked. I never would say the letter following "O" to a lady. Actually I prefer the old English term, "I'm going to see a man about a horse".

"Sir, take this cup and go into the restroom and see a man about a horse". Sounds more proper to me.