London slang is a mixture of words and phrases from around the globe. It reflects the diverse ethnic and cultural makeup of the city's population. Because London occupies such a dominant economic position in the United Kingdom, slang originally unique to the city has spread across the UK. Conversely, slang from outside London has migrated in along with people seeking work in the capital. Cockney rhyming slang and Multicultural London English is probably the best known form of London slang.
Slang can infiltrate most any element of daily life. For instance, London slang about money is believed to have been imported from India by returning servicemen during the nineteenth century. The terms monkey, meaning £500, and pony, meaning £25, are believed by some to have come from old Indian rupee banknotes, which it is asserted used to feature images of those animals (Banknotes with such denominations were issued by Bank of Bengal, Bank of Bombay and Bank of Madras and some other private banks between 1810 and 1860), however the true origin  of these terms is uncertain. Another money slang word, nicker, which means £1, is thought to be connected to the American nickel. Wonga, which describes an unspecified amount of money, may come from the Romany word for coal, wanga.
In 2005, Professor Sue Fox from Queen Mary, University of London concluded that Cockney rhyming slang was dying out because children in London are being overwhelmed by words and phrases from outside cultures. Teenagers especially are incorporating into their vocabularies new words borrowed from outside the UK. This new slang is also influenced by new technologies, especially mobile phone SMS (short message service) or text messages. While "dat" and "dere" may be of Afro-Caribbean origin along with many other terms, their use in text messages as easier-to-key options to "that" and "there/their" cement them as slang in common usage. It is also factual that there are various forms of "London Slang". Slangs spoken in multi-cultural areas of London such as Brixton, Lewisham, Peckham, Harlesden, Stonebridge, Hackney, Tottenham etc. incorporate many other terms which other areas do not use or often catch onto much later. For example terms such as: "Cah" = 'Cos = Because - e.g. "Cah di mandem wanna fly up North today." = "Because all of us want to go to North London tonight."
The large number of immigrant communities and relatively high level of ethnic integration mean that various pronunciations, words and phrases have been fused from a variety of sources to create modern London slang. The emerging dialect draws influences from Jamaican English and other Caribbean speech. This form of slang was born and is mainly spoken in Inner London and has been popularised by UK Rap music. Although the slang has been highly influenced by black immigrant communities, a large number of teenagers of all ethnicities in London have adopted it. Popular slang words include sick ("good"), bare ("very", "a lot of"), alie ("indeed", or to encourage agreement), skeen or seen ("I concur", "I believe you"), long ("boring", "repetitive"), wallad ("fool"), peak ("very bad"), sket (short for the Afro-Caribbean phrase Skettel, meaning a loose woman), slag/slut ("derogatory term for promiscuous women."), wah gwarn [wag1, wagwharn] ("what is happening", "hello"), wavey ("cool"), badman ("thug"), jezzy (a "loose woman" (from Jezebel)), ting ("thing", or, when pluralised, to refer to a current situation), safe ("trustworthy", "good", "goodbye" or to show agreement), zoot ("marijuana/tobacco cigarette"), butters ("ugly", "negative" or generally "bad"), peng ("attractive" i.e. a peng girl), clapped (ugly), leng ("weapon"), piff ("above average", or "attractive", derived from a strain of marijuana), nang ("cool", or "desirable"), dutty ("dirty"), allow it ("leave it be"), blood ("friend"), two twos nah ("obviously"), to chirpse ("to flirt"), dun know [danoe] (from "don't know", used as encouragement), yard ("house"), wasteman ("waster, scumbag"), motive ("party, event"), yai ("no"), tight ("unlucky, unfortunate"), nekki ("failure"), flop ("failed"), ends ("neighbourhood, area"), free yard ("no one home"), man's (personal pronoun, can refer to oneself; e.g. you mans goin' der?), moist ("socially awkward, "), dry ("bland," "boring"), wetty ("embarrassing/socially inept person"), nitty ("very awkward and socially inept person") dead ("boring"), youte [yaat] ("youth, younger person aged 11-15"), youngers ("politer term to address someone younger.") olders ("respected person, aged older than yourself") and recently doob/doobie ("ugly", "negative", "bad", or "disgusting")
Other examples, include calling the police 'feds'; come from the shortened term used for federal agents (FBI) in the USA. The shortening of the names of places is also popular. The West End becomes 'West' or Kentish Town becomes 'Kentish'. An example would be the sentence "Let's go to the West End tonight, you guys, and let's steal some stuff." This becomes, "You man, come we go West tonight and rip bare shit."
- Chapman, Alan (25 July 2005). "money slang history". businessballs: glossaries/terminology. Retrieved 2010-12-07.
- "Trouble and strife for cockney rhyming slang". The Times (London). 22 August 2005. Retrieved 2007-07-17.
- "Cockney accent being swept aside in London by new hip hop-inspired dialect". 16 April 2006. Archived from the original on 2007-09-26. Retrieved 2007-07-17.
- "'Nang' takes over Cockney slang". BBC News. 11 April 2006. Retrieved 2007-07-17.
- "Black slang in the pink". 21 October 2005. Retrieved 2007-07-17.