Duden, Herkunftsw├Ârterbuch : Etymologie der deutschen Sprache
Dudenverlag [2001]
Contains etymological entires for 20,000 German words, including foreign and loan words.
Interspersed with 29 summaries (in German) of the main linguistic and philological changes and developments in the history of the German language.
GE DICO 10 Open access