The man who created Roget’s Thesaurus is Peter Mark Roget. He was born in London in 1779. He had a long and distinguished career as a doctor, he lectured, he invented a slide rule that did complex mathematics, he studied optics and made an important breakthrough in understanding how the retina perceives images.
But when he retired, he came back to his pet project, a compilation of 15,000 words arranged in categories. He had started a project classifying words while he was still in his 20s, and he worked on it for almost 50 years, finally publishing his manuscript as Roget’s Thesaurus of English Words and Phrases Classified and Arranged So as to Facilitate the Expression of Ideas and Assist in Literary Composition (1852).
Roget’sThesaurus has never been out of print and now contains more than a quarter of a million words.