According to Holiday Insights, today is Thesaurus Day because it is the birth date of Peter Mark Roget (1779), the author of the reference book Roget’s Thesaurus.
Roget was a British doctor, theologian, and lexicographer (dictionary writer in a practical and theoretical sense). He was so obsessed with making lists that his family and friends noted it as a character trait as early as eight years old. His lists were thought to help battle his depression, a result (in part) of grief–his father and wife died young and evidently an uncle committed suicide in his presence.
Most of Roget’s life was focused on a concern about medical education, and he helped to found the School of Medicine at the University of Manchester.
Around 1805, Roget began compiling the list that was to eventually become the Thesaurus. When he retired in 1840, he devoted many years to getting this “list” ready for publication. When it was published in 1852, it was called Thesaurus of English Words and Phrases Classified and Arranged so as to Facilitate the Expression of Ideas and Assist in Literary Composition.
To Roget, the thesaurus was a coping mechanism. To the rest of the world, the Thesaurus has become an invaluable tool for writers and students wanting (or needing) to expand their vocabularies.