Green’s Dictionary of Slang

until the last dog dies phr.

(US) till the very end.

1860		Wyandot Pioneer (Upper Sandusky, OH) 13 Sept. 2/3: We have made up our mind to stay with Warren P. Noble [...] ‘until the last dog is hung’.
1872		Sioux City Jrnl (IO) 4/4: The officers returned to the fort at an early hour, but the citizens staid with us till the last dog was hung and a right royal time was had.
1883		Caldwell Advance (KS) 8 Feb. 2/3: It [i.e. the House of Representatives] would support the House bill to the bitter end, or until the last dog is hung.
1890		Osawatomie Graphic (KS) 19 Sept. 2/1: It is deplorable that the congress of the united states should hang on till the very last dog is hung [...] and accomplish so little.
1902		S.E. White Blazed Trail 251: It was a point of honor with them to stay ‘until the last dog was hung.’ He who deserted in the hour of need was not only a renegade , but a fool.
1937		(con. WW1) E.C. Parsons Great Adventure 175: No matter what happened, Didier was going to be there till the last dog was hung.
1964		E. Proxmire One Foot in Wash. 58: Back home, the honor guest is expected to stay until the last dog is hung!
1966		(con. c.1950) H.S. Truman Public Messages, Speeches, etc. 173: When I start anything I never give up until the last ‘dog’ dies.
1978		M.F.K. Fisher Considerable Town 168: On the other hand, the pubs and bistros are open and crowded from early on the Great Day until the last dog dies.
1988		Haney & Knowles Women and Farming 206: Mennonites hang on to land until the last dog dies. They don’t sell unless they have to, and then it’s to someone in the family.
1988		(con. c.1970) D.A. Willson REMF 291: I’m going to keep typing until the last dog is hung, or whatever.