Source : Webster's Revised Unabridged Dictionary (1913)

Evenfall \E"ven*fall`\, n.
   Beginning of evening. ``At the quiet evenfall.'' --Tennyson.

Source : WordNet®

evenfall
     n : the time of day immediately following sunset; "he loved the
         twilight"; "they finished before the fall of night" [syn:
          {twilight}, {dusk}, {gloaming}, {nightfall}, {fall}, {crepuscule},
          {crepuscle}]