The Collaborative International Dictionary of English v.0.48:

Mattoir \Mat*toir"\, n. [F. matoir.] (Engraving)
   A kind of coarse punch with a rasplike face, used for making
   a rough surface on etching ground, or on the naked copper,
   the effect after biting being very similar to stippled lines.
   [Webster 1913 Suppl.]