Conk Hairdo refers to a hairstyle that originated in the 1920's and was stylized by entertainer Cab Calloway.
The Conk style was an attempt by Black males to straighten their hair to make it look like that of White men, and was accomplished by enduring a truly painstaking process of "relaxing" the hair with a solution dominated by lye, the process which was portrayed in the movie Malcolm X. In order to keep the humidity from causing the hair to return to its natural curly state, men would wear fabric on their heads called do-rags.
The Conk faded by the mid-60's as most entertainers and therefore the general public began to move towards a more "natural" look which emphasized pride in Black heritage, a look that would eventually evolve into the Afro.