Has anyone researched into this? My family are Urdu speaking, originally from western Bihar. Recently, I was shocked (exaggeration) to find out that some words we use are not standard Urdu/Hindi. For example, for the word 'kiss' we use 'muchi' which apparently is a Bihari word (not sure if it's Bhojpuri exactly). The standard word in Urdu for kiss on the other hand is 'bosa' or so I've been told. Just an interesting point into my own family linguistics.