Source : Webster's Revised Unabridged Dictionary (1913)

Etymologist \Et`y*mol"o*gist\ ([e^]t`[i^]*m[o^]l"[-o]*j[i^]st),
   n. [Cf. F. ['e]tymologiste.]
   One who investigates the derivation of words.

Source : WordNet®

etymologist
     n : a lexicographer who specializes in etymology