It is an ‘aesthetic’ or ‘lifestyle’ theory of language and ethnicity proposed by the British sociolinguist John C. Maher.
In this perspective, language should not to be viewed as an enduring ethnic essence but a lifestyle ‘accessory.’ It is portable.
Cool actively disconnects the ‘natural’ linkage that is often made between ethnicity and language.
In such person-driven identity traditional language is optional -not rejected but bracketed.
It involves cultural crossing, self-definition made up of borrowing and bricolage of blurred ‘identities’, what one might term ‘metroethnicity’.