A version of the song is found in Carl Sandburg's "American Songbag" (1927) with the title "Man Goin' Roun'". It is also in Vance Randolph's "Ozark Folksongs" with the title "The Angel of Death". Randolph collected it in 1921 from Mr Enos Calkins in Little Rock, Arkansas. Calkins said he learned it in Missouri from a man named Wilks in the late 1890's. So it definitely predates the Nixon era.