An affectionate name for "grandmother," (esp. a somewhat
cold, possibly drunk grandmother with aspirations of social standing.)
On the
television show Arrested Development, Maeby Fünke and
George-Michael Bluth call their grandmother (Lucille Bluth) "Gangy" in many instances.
The etymology is unclear but it's frequent use in context makes the meaning clear. The spelling "Gangy" seems to be the generally-agreed upon spelling on Wikipedia, IMDB, and most TV sites.
George Michael Bluth: "Was that Gangy who was just… " (slips on Lucille's spilled
martini and falls)
Michael Bluth: "You all
right? Sorry. Your grandmother had a little accident here."
George Michael Bluth: "Oh. Does that means she's gonna have to come live with
us?"