“Grose was one of a very small band of writers to explore popular culture at that time,” Dent tells BBC Culture. “His was the first real ‘underground’ dictionary, compiled on evidence from the streets rather than the pages of literary works.”

Crude awakening

While it was pioneering in its approach, the dictionary was also one of a long line of works that aimed to define the jargon of those on the fringes of society. Coleman, who is a professor at the University of Leicester and founder of the International Society for Historical Lexicography, tells BBC Culture: “In 1567, a man called Thomas Harman published a word list that was supposedly the secret language of beggars – and then over the next couple of centuries, the same list was presented as the secret language of criminals in London; then of highwaymen; and then of gypsies.” When Grose published his book, she says, it presented some words that were “already over 200 years old”.

Yet their motivations were very different. “Harman was a magistrate, and he said that his reason for collecting this language was because con artists were roaming around the country, trying to trick decent honest folk into giving them money – and they used a secret language to communicate among themselves,” says Coleman. “He hauled these people in front of him and threatened to whip them if they didn’t tell him their secret language.”

In contrast, “Grose was a professional antiquarian – he made a living by publishing books… and he had a particular taste for things that were rude. When he went through his sources… anything to do with sex was guaranteed to get into his dictionary.”

Some of the lewder entries include ‘Clicket: Copulation of foxes; and thence used, in a canting sense, for that of men and women’ and ‘Beard splitter: A man much given to wenching’. Grose often gave lengthy explanations: ‘Clap, a venereal taint. He went out by Had’em, and came round by Clapham home; ie he went out a wenching, and got a clap’.

He wasn’t above self-censorship, as Coleman describes in her book. “Sometimes single letters are obscured or omitted, with an increasing proportion of letters obscured according to the obscenity of the word.” And Grose refused to define some of the most obscene terms, such as ‘Bagpipe: to bagpipe, a lascivious practice too indecent for explanation’.

Rebel without a clause

His interest wasn’t just prurient, Coleman tells BBC Culture. “In the late 18th Century, people are starting to think about polite behaviour and what sort of things you should be able to talk about in company – and Grose was reacting against all of that by being as vulgar as he possibly could, and absolutely revelling in it.”

It was a sensibility that appealed to the Scottish poet Robert Burns. The pair met in 1789, becoming friends – Burns even wrote a poem about Grose. “They positioned themselves in opposition to a society that was becoming more and more proper and correct, and liked to see themselves as rebels and outsiders,” says Coleman.