Just to clarify-Donuel's 14 Apr 07 - 10:07 PM post is not correct.

"Nappy" refers to the texture {'grade'} of hair and not the length of that hair.

I've no information about the etymology of the word "nappy" and "naps" as they refer to the natural state of Black people's hair.
{The individual tightly curled hair strands are called "naps"}

However, it should be noted that not all Black people have nappy hair. And some non-Black people have nappy hair.

Most African Americans prefer not to use the term 'nappy'. Black Americans also usually don't like the term "kinky" to describe their {our} hair. "Frizzy" is somewhat accepted. I've also seen some Black writers use the the term "coarse" as a descriptor of pre-straightened Black people's hair.

However, probably the term that is the most acceptable is "tightly curled" .