"rope-like strands of hair formed by matting or braiding," 1960, from dread (adj.) + locks (see lock (n.2)). The style is said to be based on that of East African warriors. So called from the dread they presumably aroused in beholders, but Rastafarian dread (1974) also has a sense of "fear of the Lord," expressed in part as alienation from contemporary society.
<a href="https://www.etymonline.com/word/dreads">Etymology of dreads by etymonline</a>
Harper, D. (n.d.). Etymology of dreads. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/dreads