Green’s Dictionary of Slang

(Aus.) Adelaide.

1905		Port Pirie Recorder (SA) 18 Oct. 4/3: Adelaide doesn't altogether mind being called Tortoise Town; it mentions in reply that the Tortoise beat the Hare.
1910		Dly Herald (Adelaide) 10 Dec. 10/2: And yet some rude strangers have been known to call ours the slowly city and Tortoise town!
1923		Register (Adelaide) 2 July 5/6: From ‘TORTOISE TOWN’:— For the championship ‘go slow’ stakes, I beg to nominate the officials who are responsible for the delayed opening o£ the Municipal Golf House.