Green’s Dictionary of Slang

(US black) a lover, a sweetheart.

1942		Pittsburgh Courier (PA) 22 Aug. 7/6: My last heart beat — (my sweetheart).
1947		M.H. Boulware Jive and Sl.

(US prison) the final walk of a condemned man from death row to the execution chamber; also attrib.

1932		L.E. Lawes Twenty Thousand Years in Sing Sing 316: She trod the ‘last mile’ bravely, if not with dignity.
1940		L.L. Stanley Men at Their Worst 46: I firmly believe that the protracted ‘last mile’ walk for condemned men is the worst form of torture that can be applied to them.
a.1953		‘Death Row’ in D. Wepman et al. Life (1976) 118: Those are memories from long before my trial, / And now it’s time to walk that last mile.
1989		J. Morton Lowspeak.

(US black) death.

1944

‘Jiver’s Bible’ in D. Burley Orig. Hbk of Harlem Jive.

(US prison) a condemned man’s final walk to the execution chamber.

1931		G. Milburn ‘Convicts’ Jargon’ in AS VI:6 439: Last Waltz, n. The final walk of a condemned man; the walk from the death house.
1936		Mencken Amer. Lang. (4th edn) 581: In virtually all American prisons [...] The march to the electric-chair is the last waltz.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 122/1: Last waltz, the. The march of the condemned man to gallows, chair, gas chamber, or other place of execution.
1992		Bentley & Corbett Prison Sl. 105: Last Waltz A condemned prisoner’s walk from the death cell to the execution chamber.

see part that goes over the fence last n.