In the 1950s and early 1960s, Charles Schultz, the cartoonist responsible for the Peanuts strip, used to draw characters (especially Lucy and Violet) sticking their tongues out and saying "Nyaah!" For example, a strip from August 2, 1965, runs as follows:
Frame 1: Lucy sticks out her tongue and says "Nyaah!" while Violet sticks out her tongue and says "Nyaah! Nyaah! Nyaah!"
Frame 2: Violet walks away with a crabby look on her face [no speech or thought bubble].
Frame 3: Violet encounters Charlie Brown and says "And Nyaah to you too!"
Frame 4: Charlie Brown, by himself, says "This is a tough neighborhood. You never know when you're going to get hit with a stray 'Nyaah'!"
In southern Texas (Corpus Christi and Houston), in roughly the same time period (early and mid-1960s), I can remember hearing other children chant, in a sing-song voice, "Nyaah! Nyaah! Nyaah! Nyaah! Nyaah!" with the emphasis on the fourth "Nyaah!" The point of the expression was more often than not to express the idea "I have something that you don't," but it could also be used in other situations to indicate scorn, mockery, or malice.
Much later, in their 1982 single "I Know What Boys Like," the Waitresses offer an updated version of "Nyaah! Nyaah! Nyaah! Nyaah! Nyaah!" (at 1:58 and again at 2:55 of the video), but their rendition isn't nearly as syncopated as the real-life version I remember from my childhood.