DISCLAMER I do not condone the use of derogatory terms. I am purely interested in this from an academic sense.

For those of you that don't know nappy is a term used to describe the hair of people of African origin and is commonly seen as derogatory. I'm looking into the etymology of the term because I'm interested to see if it connects to the use of nappy to mean diaper. This diaper meaning usage is common in the UK, Australia, New Zealand, South Africa and Ireland from what I can tell. I've found a wikipedia entry saying

"These words (nappy and bushy) were originally used by slaveowners, as far back as the 1800s, to grotesquely describe the hair of their slaves." citing

West, Willis (1922). History of the American People. Boston, MA.: Allyn and Bacon. p. 1-819.

but I can't find that book or other sources beyond wikipedia or a few nerd mom blogs about the use of nappy vs diaper and dont cite any sources. Basically I'm wondering if the term originated as calling someone shit head cause babies shit in diapers and the hair is on their head or something to that extent. I know that the US wasn't on the list of countries that use nappy to mean diaper but it may have been in the 1800's and then diaper replaced it as the derogatory term took primary definition locally.