Source : Webster's Revised Unabridged Dictionary (1913)

Derivation \Der`iva"tion\, n.
   The formation of a word from its more original or radical
   elements; also, a statement of the origin and history of a
   word.

Derivation \Der`i*va"tion\, n. [L. derivatio: cf. F.
   d['e]rivation. See {Derive}.]
   1. A leading or drawing off of water from a stream or source.
      [Obs.] --T. Burnet.

   2. The act of receiving anything from a source; the act of
      procuring an effect from a cause, means, or condition, as
      profits from capital, conclusions or opinions from
      evidence.

            As touching traditional communication, . . . I do
            not doubt but many of those truths have had the help
            of that derivation.                   --Sir M. Hale.

   3. The act of tracing origin or descent, as in grammar or
      genealogy; as, the derivation of a word from an Aryan
      root.

   4. The state or method of being derived; the relation of
      origin when established or asserted.

   5. That from which a thing is derived.

   6. That which is derived; a derivative; a deduction.

            From the Euphrates into an artificial derivation of
            that river.                           --Gibbon.

   7. (Math.) The operation of deducing one function from
      another according to some fixed law, called the law of
      derivation, as the of differentiation or of integration.

   8. (Med.) A drawing of humors or fluids from one part of the
      body to another, to relieve or lessen a morbid process.

Source : WordNet®

derivation
     n 1: the source from which something derives (i.e. comes or
          issues); "he prefers shoes of Italian derivation"
     2: (historical linguistics) an explanation of the historical
        origins of a word or phrase [syn: {deriving}, {etymologizing}]
     3: a line of reasoning that shows how a conclusion follows
        logically from accepted propositions
     4: (descriptive linguistics) the process whereby new words are
        formed from existing words or bases by affixation:
        `singer' from `sing'; `undo' from `do'
     5: inherited properties shared with others of your bloodline
        [syn: {ancestry}, {lineage}, {filiation}]
     6: drawing of fluid or inflammation away from a diseased part
        of the body
     7: drawing off water from its main channel as for irrigation