Polichinelle (in French or Pulicinella in Italian) is one of the characters of the Commedia dell'arte. I don't know what his character is or what his personality is, but you could easily look it up somewhere (ie Wikipedia)I'm guessing the piece is a character piece, reflecting the personality of Pulichinella.
I have another question about this piece.There are some rather large spans in this piece in the left hand. On page 7-8 I think, the left hand has a few 10ths. I can't reach this, obviously. Should I bounce off the bottom note and get to the top as fast as possible? The piece is rather fast so I don't know if it'd be noticed.
On measure 11-12/102-103, you will notice that Rachmaninoff plays fairly slowly, then on the third measure of the set (13/104), he accelerates to something close to presto. That makes it easier to handle the large jumps, and adds excitement to the piece.