Galah

Where "Galah" Comes From

"Galah" — used to mean a fool or idiot, someone who talks loudly and says little worth hearing — takes its name from the galah cockatoo (Eolophus roseicapilla), one of Australia's most common and loudest birds. The bird's name comes from the Yuwaalaraay language of northern New South Wales, where the word "gilā" described the pink and grey cockatoo. It was first recorded in English in 1862, in explorer John McKinlay's Journal of Exploration in the Interior of Australia, in early spellings including "galar" and "gillar."

The slang sense — a noisy fool — is recorded from the 1930s, deriving from the galah's well-known habit of gathering in large, raucous, wheeling flocks and producing relentless noise apparently uncorrelated with useful communication. The galah is, in reality, an intelligent and social bird capable of learning words and problem-solving; its reputation in slang as a symbol of vacant noise-making is a case of sound overriding substance. "Don't be such a galah" is one of the more affectionate Australian insults, carrying a lightness that heavier words like "drongo" do not.

Source: Australian National Dictionary Centre — "pet shop galah"