Jacob Grimm was born 4 January 1785, in Hanau in Hesse-Kassel. His father, Philipp Grimm, was a lawyer who died while Jacob was a child, and his mother was left with a very small income. Her sister was lady of the chamber to the Landgravine of Hesse, and she helped to support and educate the family. Jacob was sent to the public school at Kassel in 1798 with his younger brother Wilhelm.

In 1802, he went to the University of Marburg where he studied law, a profession for which he had been intended by his father. His brother joined him at Marburg a year later, having just recovered from a severe illness, and likewise began the study of law.

In 1808, soon after the death of his mother, he was appointed superintendent of the private library of Jérôme Bonaparte, King of Westphalia, into which Hesse-Kassel had been incorporated by Napoleon. Grimm was appointed an auditor to the state council, while retaining his superintendent post. His salary rose to 4000 francs and his official duties were nominal. In 1813, after the expulsion of Bonaparte and the reinstatement of an elector, Grimm was appointed Secretary of Legation accompanying the Hessian minister to the headquarters of the allied army. In 1814, he was sent to Paris to demand restitution of books taken by the French, and he attended the Congress of Vienna as Secretary of Legation in 1814–1815. Upon his return from Vienna, he was sent to Paris again to secure book restitutions. Meanwhile, Wilhelm had obtained a job at the Kassel library, and Jacob was made second librarian under Volkel in 1816. Upon the death of Volkel in 1828, the brothers both expected promotion, and they were dissatisfied when the role of first librarian was given to Rommel, the keeper of the archives. Consequently, they moved the following year to the University of Göttingen, where Jacob was appointed professor and librarian, and Wilhelm under-librarian. Jacob Grimm lectured on legal antiquities, historical grammar, literary history, and diplomatics, explained Old German poems, and commented on the Germania of Tacitus.

Grimm’s text-editions were mostly prepared in conjunction with his brother. In 1812 they published the two ancient fragments of the Hildebrandslied and the Weißenbrunner Gebet, Jacob having discovered what till then had never been suspected — namely the alliteration in these poems. However, Jacob had little taste for text editing, and, as he himself confessed, working on a critical text gave him little pleasure. He therefore left this department to others, especially Lachmann, who soon turned his brilliant critical genius, trained in the severe school of classical philology, to Old and Middle High German poetry and metre.

Grimm’s famous Deutsche Grammatik (German Grammar) was the outcome of his purely philological work. He drew on the work of past generations, from the humanists onwards, consulting an enormous collection of materials in the form of text editions, dictionaries, and grammars, mostly uncritical and unreliable. Some work had been done in the way of comparison and determination of general laws, and the concept of a comparative Germanic grammar had been grasped by the Englishman George Hickes by the beginning of the 18th century, in his Thesaurus. Ten Kate in the Netherlands had made valuable contributions to the history and comparison of Germanic languages. Grimm himself did not initially intend to include all the languages in his Grammar, but he soon found that Old High German postulated Gothic, and that the later stages of German could not be understood without the help of other West Germanic varieties including English, and that the literature of Scandinavia could not be ignored. The first edition of the first part of the Grammar, which appeared in 1819, treated the inflections of all these languages, and included a general introduction in which he vindicated the importance of a historical study of the German language against the quasi-philosophical methods then in vogue.

In 1822 the book appeared in a second edition (really a new work, for, as Grimm himself says in the preface, he had to “mow the first crop down to the ground”). The considerable gap between the two stages of Grimm’s development of these editions is shown by the fact that the second volume addresses phonology in 600 pages – more than half the volume. Grimm had concluded that all philology must be based on rigorous adherence to the laws of sound change, and he subsequently never deviated from this principle. This gave to all his investigations a consistency and force of conviction that had been lacking in the study of philology before his day.

Both Brothers were attracted from the beginning by all national poetry, whether in the form of epics, ballads or popular tales. They published In 1816–1818 a collection of legends culled from diverse sources and published the two-volume Deutsche Sagen (German Legends). At the same time they collected all the folktales they could find, partly from the mouths of the people, partly from manuscripts and books, and published in 1812–1815 the first edition of those Kinder- und Hausmärchen (Children’s and Household Tales), which has carried the name of the brothers Grimm into every household of the western world. The closely related subject of the satirical beast epic of the Middle Ages also held great charm for Jacob Grimm, and he published an edition of the Reinhart Fuchs in 1834. His first contribution to mythology was the first volume of an edition of the Eddaic songs, undertaken jointly with his brother, and was published in 1815. However, this work was not followed by any others on the subject.

The first edition of his Deutsche Mythologie (German Mythology) appeared in 1835. This work covered the whole range of the subject, attempting to trace the mythology and superstitions of the old Teutons back to the very dawn of direct evidence, and following their evolution to modern-day popular traditions, tales, and expressions.

Grimm joined other academics, known as the Göttingen Seven, who signed a protest against the King of Hanover’s abrogation of the liberal constitution which had been established some years before. As a result, he was dismissed from his professorship and banished from the Kingdom of Hanover in 1837. He returned to Kassel with his brother, who had also signed the protest. They remained there until 1840, when they accepted King Frederick William IV’s invitation to move to the University of Berlin, where they both received professorships and were elected members of the Academy of Sciences. Grimm was not under any obligation to lecture, and seldom did so; he spent his time working with his brother on their dictionary project. During their time in Kassel, he regularly attended the meetings of the academy and read papers on varied subjects, including Karl Konrad Friedrich Wilhelm Lachmann, Friedrich Schiller, old age, and the origin of language. He described his impressions of Italian and Scandinavian travel, interspersing more general observations with linguistic details. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1857.

Grimm’s monumental dictionary of the German Language, the Deutsches Wörterbuch, was started in 1838 and first published in 1854. The Brothers anticipated it would take 10 years and encompass some six to seven volumes. However, it was undertaken on so large a scale as to make it impossible for them to complete it. The dictionary, as far as it was worked on by Grimm himself, has been described as a collection of disconnected antiquarian essays of high value. It was finally finished by subsequent scholars in 1961 and supplemented in 1971. At 33 volumes at some 330,000 headwords, it remains a standard work of reference to the present day. A current project at the Berlin-Brandenburg Academy of Sciences and Humanities is underway to update the Deutsches Wörterbuch to modern academic standards. Volumes A–F were scheduled for release in 2012.

The Grammar was continued in three volumes, treating principally derivation, composition and syntax, the last of which was unfinished. Grimm then began a third edition, of which only one part, comprising the vowels, appeared in 1840, his time being afterwards taken up mainly by the dictionary. The Grammar is noted for its comprehensiveness, method and fullness of detail, with all his points illustrated by an almost exhaustive mass of material, and it has served as a model for all succeeding investigators. Diez’s grammar of the Romance languages is founded entirely on Grimm’s methods, which have had a profound influence on the wider study of the Indo-European languages in general.

Jacob Grimm died on 20 September 1863, in Berlin, Germany from disease.