I am so very offended by these do-gooders sterilizing quaint colloquialisms. A niggerhead, in the western vernacular, is a big, rounded rock or outcropping - and can mean anything from a large stone in a road to a feature on a mountain. I doubt it has a racial connotation at all, and if it did have any, it is long gone. It probably comes from sea faring folks' use of the word for coral outcroppings, and that (since they can tie to it), from the bollard.
Lord help us if we ever went hunting 'chinks' (the Chinese pheasant is called a 'chink' all over the west)... or 'injun'd up on something... MANY colloquialisms are offensive at their root, and language is made cheaper without them.
It always struck me that the term "German engineering" can be used with pride in automobile marketing campaigns. Yet, if one were to refer to "African engineering", the PC police would be all over that individual.