As to the word 'conk'.

Once upon a time there was a product in the United States that was called "Conkalene'. Conkalene was
a lye based grease used to straighten African American men's [and women's hair.

So a Black person who had a 'conk' had their hair straightened with Conkalene [I might be spelling it wrong.I'm not sure}.

Spike Lee's Malcolm X movie has a great scene based on the book on Malcolm X before he became a Muslim 'conking' his hair ['conking' meaning using Conkalene]. And to protect your conk at night you might wear a do-rag {a rag/scarf to protect your hair do {the hair that was 'done'??} Of course most people just used the foot of nylon stockings as a covering for their hair, putting this on before going to bed..

Currently products [called 'perms' I suppose from 'permanent', though they are anything but permanent] used to straighten tightly curly hair don't contain lye. They haven't since the mid 1960s.

Still if you aren't careful, those perms still burn-or so I'm told..
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PS: One of the by products of having a White roomate in college was that I learned that White women perm their hair to add curls while Black women perm their hair to straighten it.

Oh, the joys of multi-cultural living!!