What is the origin of supercilious?

Arrogant and disdainful types tend to raise an eyebrow at anything they consider beneath them. The original supercilious crowd must have shown that raised-eyebrow look often, because the adjective supercilious derives from "supercilium," Latin for eyebrow. (We plucked our adjective and its meaning from the Latin adjective superciliosus.) "Supercilious" has been used to describe the censoriously overbearing since the late 1600s, but there was a time in the 1700s when it was also used as a synonym of another "supercilium" descendent, "superciliary" ("of, relating to, or adjoining the eyebrow"). Although the eyebrow sense of "supercilious" is now obsolete, it does help explain what ornithologist John Latham meant in 1782 when he described a "Supercilious K[ingfisher]" with a narrow orange stripe over its eyes.