Plural of eyetooth; the pointed canine teeth in the upper jaw, called this because they're situated directly below the eyes.
From 'eye' + 'teeth' (plural of tooth). Named anatomically because of their position under the eyes, dating to Old English with this same logic.
The phrase 'give one's eyeteeth' (meaning to sacrifice something valuable) comes from eyeteeth because these are the most prominent and visible teeth when you smile or snarl—worth so much you'd trade them, but of course you'd regret it!
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