THESAURUS 

The word 'thesaurus'  comes from Greek term 'thesauros' meaning a storehouse or treasury of  words. The Oxford English Dictionary  defines "thesaurus" as a archaeological term "a treasury  of temple, etc." and quotes its  use in 1736  as  a treasury or store house of knowledge. Dictionary defines it as "a book of words or of information  about a particular field or a set of concepts, specially a dictionary  of synonyms". A dictionary  lists words along with their meanings;  synonyms, etc. in alphabetical order, but a thesaurus assembles all words related to an idea at one place. Modern usage may be said to date from 1852 when Peter Mark Roget thought of his thesaurus as  a classification of ideas. Roget's Thesaurus had nothing to do with information retrieval. But his novel idea was later profitably employed  in the compilation of thesaurus for information retrieval. 

Helen Brownson is said to be the first person who used the term  'thesaurus' in the context of information retrieval in a paper presented at the Dorking Conference on Classification Research in 1957. H. P Luhn was probably the first person to think in" terms of information retrieval thesaurus, who suggested the compilation, for indexing purposes, of 'families of notions' and dictionary of 'notion  families'. The first thesaurus used in information retrieval system was  developed by Du Pont in USA around 1969 and since then many thesauri have been brought out in different subject fields: A number of standards have also come into existence to provide guidelines in the design and development of monolingual and multilingual: thesauri.