https://en.wikipedia.org/wiki/Chav
Etymology
Opinion is divided on the origin of the term. "Chav" may have its origins in the Romani word "chavi" ("child") or "chaval" ("boy"), which later came to mean "man". The word "chavvy" has existed since at least the 19th century; lexicographer Eric Partridge mentions it in his 1950 dictionary of slang and unconventional English, giving its date of origin as c. 1860.
The word in its current pejorative usage is recorded by the Oxford English Dictionary as first used in a Usenet forum in 1998 and first used in a newspaper in 2002. By 2005, the term had become widely used to refer to a type of anti-social, uncultured youth, portrayed as wearing excessive flashy jewellery, white athletic shoes, baseball caps, and sham designer clothes. Similarly, girls are portrayed as commonly wearing clothes which expose their midriffs.
In his 2011 book, Chavs: The Demonization of the Working Class, Owen Jones argued that the word is an attack on the poor.[12] In the 2010 book Stab Proof Scarecrows by Lance Manley, it was surmised that "chav" was an abbreviation for "council housed and violent". Others regard this as a backronym. This interpretation of the word was used in a 2012 public statement by rapper Plan B as he spoke out to oppose the use of the term.
In 2013 linguist David Crystal said on BBC Learning English:
People talk about "chav behaviour" or "chav insults" and that sort of thing. Oh, don't believe the popular etymologies that you read sometimes in the press and on websites. I saw one the other day, people said, "It's an acronym, 'chav', from 'council house and violent'"—well, no, it isn't, that was made up in recent times.
It has also been suggested that the term is derived from the name of the town of Chatham, in Kent, but the Oxford English Dictionary thinks this is "probably a later rationalization".