One afternoon I was sent to fix the VHF radio antenna for the Nuttall Styris company in downtown San Diego. As I was wrapping up, a fisherman came to the parts counter. He needed a new niggerhead for his boat. A black salesman came to the counter to serve him. The poor guy stammered and tried every way imaginable to ask for the product without using the colloquial name. Finally, the salesman exclaimed, "Oh, you want a niggerhead". The fisherman looked very relieved. He simply couldn't bring himself to use the phrase. BTW, the fisherman was white.
A similar situation occurred some weeks later at the office. We had cans of small diameter rope soaked in gooey asphalt for the purpose of sealing deck flanges. The common term for the product at the office was "monkey shit". Somebody took the last can from the stockroom and left the purchasing agent flummoxed. I need to order 10 cans of "monkey shit", but I have no idea what the real name is.".