The Collaborative International Dictionary of English v.0.48:

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]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "etymology":
   bowwow theory, comparative linguistics, derivation,
   descriptive linguistics, dialectology, dingdong theory, eponymy,
   folk etymology, glossematics, glossology, glottochronology,
   glottology, grammar, graphemics, historical linguistics,
   language study, lexicology, lexicostatistics, linguistic geography,
   linguistic science, linguistics, mathematical linguistics,
   morphology, morphophonemics, origin, paleography, philology,
   phonetics, phonology, psycholinguistics, semantic history,
   semantics, sociolinguistics, structuralism, syntactics,
   transformational linguistics, word history