Plural of haw, referring to the red berries produced by hawthorn trees, or the eyelids of horses (the nictitating membranes).
From Old English 'haga' meaning 'hawthorn' or 'hedge,' and separately from Old English 'haw' for the eye membrane. Both derive from Germanic roots related to 'hedges' and 'enclosure.'
Medieval doctors thought the haw (third eyelid) in horses was evidence that animals had built-in protection mechanisms humans lacked—they didn't realize humans have them too, just much less developed!
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