Blind-freddy Definition

pronoun

(Australia, informal) An imaginary incapacitated person held up as an archetype of incapacity: what blind Freddy can see (understand) must be very obvious. [From 1940s.]

Wiktionary

Origin of Blind-freddy

A police officer, Sir Frederick William Pottinger, who was in charge of the Lachlan district. The success of bushranger Ben Hall in evading capture there in 1862 earned Pottinger the name "Blind Freddy".

From Wiktionary
A blind hawker called Freddy or Freddie who lived in Sydney in the 1920s.

From Wiktionary