The Collaborative International Dictionary of English v.0.48:

Ingrain \In"grain`\ (?; 277), a. [Pref. in- in + grain kermes.
   See Engrain, Grain.]
   [1913 Webster]
   1. Dyed with grain, or kermes. [Obs.]
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   2. Dyed before manufacture, -- said of the material of a
      textile fabric; hence, in general, thoroughly inwrought;
      forming an essential part of the substance.
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   Ingrain carpet, a double or two-ply carpet.

   Triple ingrain carpet, a three-ply carpet.
      [1913 Webster]