Phrases.org.uk has information on the origins of popular sayings and phrases
Meanings and origins of sayings and phrases | List of sayings | English sayings | Idiom definitions | Idiom examples | Idiom origins | List of idioms | Idiom dictionary | Meaning of idioms
The Phrasefinder site was founded in 1997 by Gary Martin, who writes the Meanings and Origins section of the site and the Phrase A Week posts. It grew out of an interest in computational linguistics that was developed during his post-graduate research in 1985 and later while working in an IBM-financed research project at Sheffield Hallam University. That project, headed by Prof. Asher Cashdan, investigated the use of artificial intelligence techniques to aid the teaching of writing.
The site initially hosted a searchable database of phrases and idioms. Its search algorithm also uses artificial intelligence methods to provide pertinent search results.
Note: That database, called The Phrase Thesaurus found an audience amongst professional writers like journalists and copywriters. It is now available commercially, hosted by an independent site. Details, including more information on how it works, are available at that site.