The dura mater; the tough, outermost of the three membranes (meninges) that protect the brain and spinal cord.
From Latin 'dura' (hard) and 'mater' (mother). Medieval anatomists called it the 'hard mother' to contrast with softer inner membranes.
Medieval doctors used 'mother' for protective membranes because they saw them as nurturing—the three meninges were literally the 'hard mother,' 'spider mother,' and 'tender mother!'
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