The Collaborative International Dictionary of English v.0.48:

Tithingman \Tith"ing*man\, n.; pl. Tithingmen.
   1. (O. Eng. Law) The chief man of a tithing; a headborough;
      one elected to preside over the tithing.
      [1913 Webster]

   2. (Law) A peace officer; an under constable.
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   3. A parish officer elected annually to preserve good order
      in the church during divine service, to make complaint of
      any disorderly conduct, and to enforce the observance of
      the Sabbath. [Local, U. S.]
      [1913 Webster]