The Collaborative International Dictionary of English v.0.48:

Noon \Noon\ (n[=oo]n), n. [AS. n[=o]n, orig., the ninth hour,
   fr. L. nona (sc. hora) the ninth hour, then applied to the
   church services (called nones) at that hour, the time of
   which was afterwards changed to noon. See Nine, and cf.
   Nones, Nunchion.]
   1. The middle of the day; midday; the time when the sun is in
      the meridian; twelve o'clock in the daytime.
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   2. Hence, the highest point; culmination.
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            In the very noon of that brilliant life which was
            destined to be so soon, and so fatally,
            overshadowed.                         --Motley.
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   High noon, the exact meridian; midday.

   Noon of night, midnight. [Poetic] --Dryden.
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