Professor Whitney, who had been attracted by Edgren's unusual knowledge of German, invited him to be the chief collaborator in preparing a German-English dictionary which had been in the planning stage for a considerable period of time. Most of the work was done by Edgren. The strain of the dictionary project was so great that he developed a serious illness which came near proving fatal. It was reported that "for days the sufferer lay in delirium, muttering German roots and wrestling with etymologic problems." But Hjalmar's fine physical resources enabled him to overcome this crisis. The dictionary was published in New York and London in 1877 with the title, A Compendious German and English and English and German Dictionary.

~ Lindquist, An immigrant's two worlds: a biography of Hjalmar Edgren (1972)
https://archive.org/details/immigrantstwowor00lind

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more search terms: Deutsch-Englisch Wörterbuch, etymology, etymologie