This word derived from a Romany word.
Commonly used to replace the word "mate".
Despite the negative connotations this word has attracted in more recent times, this is historically a general term used in the Portsmouth dialect. It is in no way chavvy, save for the fact that most of the real Pomponians left in Portsmouth these days pretty much are chavs.
A more endearing term is "mushty" or "mushdy", often rhymed with "cushdy", which expresses more of a friendly level of acquaintance.
Mush, you got a ciggy?
Mate, did you see them mushes Jonno knocked spark out last night?
Cushdy mushdy, thanks for paying me bail.