The Collaborative International Dictionary of English v.0.48:

Cognation \Cog*na"tion\, n. [L. cognatio.]
   1. Relationship by blood; descent from the same original;
      kindred.
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            As by our cognation to the body of the first Adam.
                                                  --Jer. Taylor.
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   2. Participation of the same nature. --Sir T. Browne.
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            A like temper and cognation.          --Sir K.
                                                  Digby.
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   3. (Law) That tie of consanguinity which exists between
      persons descended from the same mother; -- used in
      distinction from agnation.
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WordNet (r) 3.0 (2006):

cognation
    n 1: line of descent traced through the maternal side of the
         family [syn: matrilineage, enation, cognation]
    2: (anthropology) related by blood [syn: consanguinity, blood
       kinship, cognation] [ant: affinity]