The Collaborative International Dictionary of English v.0.48:

Suillage \Su"il*lage\, n. [OF. souillage, soillage, fr.
   souiller, soiller. See Soil to stain, and cf. Sullage.]
   A drain or collection of filth. [Obs.] [Written also
   sulliage, and sullage.] --Sir H. Wotton.
   [1913 Webster]