This word is not registered in the DRAE, but it is common in Murcia Spain as a synonym for "ass". It seems to come from "rearguard", for "the back", but "bufa" may not be a festive suffix since among its many meanings there is one for "deaf flatulence" that can be better associated with the anus. Also, like so many words, "bufa" has been used to name the "penis", perhaps because of some association with its ancient meaning of "bladder". 2º_ Probably thanks to the immigration from Murcia, in the Rio de la Plata lunfardo it also exists but with a different meaning, since it is an adjective for pederast ("active homosexual male"). This is by association with "bufa" as an apocope of "bufarra".