Latin super (above) + cilia (eyelashes) gives supercilia (eyebrows).
Supercilia + -osus (full of) gives superciliosus (looking with disdain/raised eyebrows, lit. full of eyebrows).
During the 16th century, English writers borrowed superciliosus from Latin as supercilious. But we had to wait four more centuries for Leonard Nimoy's Spock.
