Mockney (a portmanteau of ‘mock’ and ‘Cockney’) is an affected accent and form of speech in imitation of Cockney or working class London speech, or a person with such an accent. A stereotypical Mockney comes from a middle or upper-middle class background in England’s Home Counties (the counties encircling London).
Mockney is distinct from Estuary English by being the deliberate affectation of the working-class London (Cockney) accent. A person speaking with a Mockney accent might adopt Cockney pronunciation but retain standard grammatical forms where the Cockney would use non-standard forms (e.g. negative concord / double negative). The first published use of the word according to the Oxford English Dictionary was in 1989.
It is an affectation sometimes adopted for aesthetic or theatric purposes, other times just to sound ‘cool,’ generate street credibility or give the false impression that the speaker rose from humble beginnings and became prominent through some innate talent rather than the education, contacts and other advantages a privileged background tends to bring.
Britpop band Blur was said to have ‘Blur’s mockney, down-the-dogs blokey charm.’ Mick Jagger is often accused of having been the first celebrity in modern times to overplay his regional accent in order to boost his street credibility.
One explanation of dialect adoption given in social linguistics is prestige. A person is likely to adopt speech patterns (including accent, vocabulary, dialect or even language) which they perceive as ‘prestigious.’ The concept of communication accommodation, either upwards or downwards in idiolect (a variety of a language unique to one individual person), can be seen in many social interactions.
One can put someone at ease by speaking in a familiar tone or intonation, or one can intimidate or alienate someone by speaking more formally. For example, in a courtroom, a more formal register with technical legal jargon can be used to intimidate a defendant. In contrast, Mockney seeks to lower the perceived socio-economic class of the speaker.