The Collaborative International Dictionary of English v.0.48:

Chaun \Chaun\, n.
   A gap. [Obs.] --Colgrave.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Chaun \Chaun\, v. t. & i.
   To open; to yawn. [Obs.]
   [1913 Webster]

         O, chaun thy breast.                     --Marston.
   [1913 Webster]