The Collaborative International Dictionary of English v.0.48:

Purism \Pur"ism\, n. [Cf. F. purisme.]
   Rigid purity; the quality of being affectedly pure or nice,
   especially in the choice of language; over-solicitude as to
   purity. "His political purism." --De Quincey.
   [1913 Webster]

         The English language, however, . . . had even already
         become too thoroughly and essentially a mixed tongue
         for his doctrine of purism to be admitted to the
         letter.                                  --Craik.
   [1913 Webster]

WordNet (r) 3.0 (2006):

purism
    n 1: scrupulous or exaggerated insistence on purity or
         correctness (especially in language); "linguistic purisms"