etymology
    n 1: a history of a word
    2: the study of the sources and development of words

Etymology \Et`y*mol"o*gy\ (-j[y^]), n.; pl. Etymologies
   (-j[i^]z). [L.etymologia, Gr. 'etymologi`a; 'e`tymon etymon +
   lo`gos discourse, description: cf. F. ['e]tymologie. See
   Etymon, and -logy.]
   1. That branch of philological science which treats of the
      history of words, tracing out their origin, primitive
      significance, and changes of form and meaning.
      [1913 Webster]

   2. That part of grammar which relates to the changes in the
      form of the words in a language; inflection.
      [1913 Webster]