From the website:
The paramount project of the Academy of the Hebrew Language is the Historical Dictionary; the creation of this enormous and most important enterprise was decided upon shortly after the Academy was established in 1953.
The aim of a historical dictionary is to relate the history of the words of a language by answering questions such as: When did the word first enter the language, and is it still in use? What were the word’s original form and meaning and how did they change over time?
Good answers to such questions require a large database of texts of the different historical language strata, set in a concordance form, i.e. each word is linked to its relevant dictionary-entry.
The Historical Dictionary Project has accumulated texts of all the extant Hebrew compositions from the time of the canonization of the Hebrew Bible until the end of the Geonic period, and large selections of Hebrew literature from the mid-18-th century until the founding of the State of Israel. In recent years medieval compositions have begun to be processed into the database.
After over fifty years of scholarly work done by scores of experts in Hebrew linguistics, literature and other Judaic Studies, there has emerged a unique treasure of scholarly concordances to Hebrew Literature, in the form of the present database offered to the public in this site.