Other forms: eyebrows
An eyebrow is the line of hair above each eye. You raise them when surprised and lower them when cross.
They keep sweat out of the eyes, which is the practical job, but their real work is signalling, since eyebrows carry an enormous amount of human expression. The idioms follow: raising an eyebrow means showing surprise or mild disapproval, and something that raises eyebrows causes talk. Grooming has made them an industry of their own, with threading, tinting and pencilling. The word is one word.
1nouneyebrowThe strip of hair above the eye.
“He raised one eyebrow and said nothing.”
Old English
ēaganbrū — eyebrow
Middle English
eȝebreu
English, today
eyebrow
From Middle English eȝebreu, alteration of Old English ēaganbrū (“eyebrow”), equivalent to eye + brow. The corresponding Old English ēagbrǣw meant "eyelid". Compare Dutch oogbrauw (“eyelid; eyelash; eyebrow”), German Augenbraue (“eyebrow”).
Etymology from Wiktionary, CC BY-SA