The Collaborative International Dictionary of English v.0.48:

Proin \Proin\ (proin), v. t. [See Prune to trim.]
   To lop; to trim; to prune; to adorn. [Obs.] --Chaucer.
   [1913 Webster]

         The sprigs that did about it grow
         He proined from the leafy arms.          --Chapman.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Proin \Proin\, v. i.
   To employed in pruning. [Obs.]
   [1913 Webster]