Why the name 'Rats of Tobruk'?

 A former British citizen William Joyce, better known as Lord Haw-Haw, was a notorious broadcaster of Nazi propaganda to the UK during World War II. His announcement ‘Germany calling, Germany calling’ was a familiar sound across the airwaves, introducing threats and misinformation which he broadcast from his Hamburg base. 

During broadcast about the Tobruk siege, Joyce scoffed that the men defending the garrison were ‘caught like rats in a trap’ and often referred to them as poor desert rats of Tobruk, who live like rats and will die like rats. The Australian soldiers loved the term ‘Rats of Tobruk’ and defiantly adopted the term as a badge of honour. Calling themselves the ‘Rats of Tobruk’, they turned the derogatory comments back against the Germans. They were very proud of their new name. 

William Joyce was eventually captured and returned to Britain, where he was later hanged for treason in January 1946. 

William Joyce, his alias was Lord Haw-Haw
One of the first Tobruk Medals, said to have been made by Australian diggers whilst in Tobruk. The ubiquitous desert rat at the centre of the design.
William Joyce in Nazi uniform