Dr Johnson famously took nine years to write his dictionary, but the biggest thesaurus in the world will be published this autumn after a labour of love spanning five decades.

Work on the Historical Thesaurus of the Oxford English Dictionary began in 1965. The mammoth enterprise has survived fire and funding problems and has had to be constantly updated to incorporate new words.

With 800,000 meanings for 600,000 words organised into more than 230,000 categories and subcategories, the thesaurus is twice the size of Roget’s version.

It contains almost the entire vocabulary of English, from Old English to the present day, giving a unique insight into the development of the language.

The project began 44 years ago with Michael Samuels, then Professor of English Language at the University of Glasgow. Several of the project’s founders have since died.

His team began transcribing information from the 20-volume Oxford English Dictionary (OED) on to slips of paper.

They plugged away for more than a decade, and disaster almost struck in 1978 when the building housing the only copy of their work caught fire.

The entire building was gutted, but the slips remained intact because they were stored in metal filing cabinets.

After that the slips were written in triplicate and stored in three different locations.

As technology developed, the work in progress was microfilmed, and eventually computers were used.

The thesaurus neared completion in 1980, but the team then took the decision to include material from updated versions of the OED. This added almost another 30 years to the task, including words such as “speed-dating”.

Its publisher, Oxford University Press, claims that it is the first historical thesaurus in any language, and will become an invaluable study resource.

The publisher described the work as having surmounted a series of “intellectual, financial and domestic challenges”.

Christian Kay, one of the four coeditors, began working on the project in the late 1960s, when she was 27. She also became a lecturer in the English language department of the University of Glasgow.

Professor Kay, now 69, said: “I started on this as a research assistant — I didn’t think at the time I would be involved 40 years later.

“Initially there were just two of us, myself and Irené Wotherspoon, collecting data. We put in most words from the dictionary, but had to decide where they fitted.

“We started off using Roget’s classifications but it soon became apparent that wasn’t adequate, as it wasn’t detailed enough.

“Then we virtually started from scratch with a new system. That’s why it took so long.

“Fundraising produced all sorts of cliffhangers — people didn’t know if they would get paid or not. Just as the money was about to run out, you would get a little bit more from one academic foundation or another.

“The youth employment schemes in the 1980s were a stroke of luck for us, because we took on people to input the data on word processors. We had all sorts of people coming through, and all sorts of academics from other universities who did bits of work for us.

“It was a very circular process, with disagreements between people about where to put a word, for example, whether ‘sin’ should go in religion or as a general concept.

“We became obsessive about it. At various points we could have given up but we were determined to get it finished. There were always people urging us to keep going.”

Of the fire, Professor Kay said: “We still have boxes of old Oxford English Dictionaries that survived the fire that are singed around the edge and smell of smoke.”

The thesaurus is divided into three major sections: the external, mental and social worlds.

The 354 categories cover subjects including leisure, authority, education, faith, armed hostility, philosophy, mental capacity, aesthetics, sleeping and waking, matter, the supernatural and relative properties.

Volume 1 is the thesaurus itself, organised according to semantic categories, while Volume 2 is an alphabetical index listing most of its synonyms.

Eventually the project will be linked online with the Oxford English Dictionary, but a date for its completion has yet to be determined.

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