Peter Mark Roget

Peter Mark Roget was a physician who had kept a private list of words grouped by meaning since his twenties. After retiring from medicine he expanded it into the Thesaurus of English Words and Phrases, published in 1852 when he was 73. He kept revising it through dozens of printings until his death at 90, and his family carried the work on. It is a fine example of a private habit becoming a public reference.