Digging thru my research, here's my take on it all. Feel free to play with my timeline....

After the Post-Dispatch coined the sensationalistic name in 1891 it bounced around in random newspapers for a few decades. It looks like it became popularized/gathered steam as a result of interest in Jesse James picking back up around 1930, probably due to Saturday matinee movies, radio shows and comic books. What better way to have America's most noted outlaw get his start than under a man with the gory name of Bloody Bill?

It doesn't look like the phrase was showing up in any books until the 1930s, at which time pulp fiction-type tomes picked it up--"The Distant Prize" by Charles Joseph Finger in 1935 and "Bushwhacker" by George Clinton Arthur in 1938.

Then there were a couple more in the 1940s, "Belle Starr" by Burton Rascoe in 1941 and "The Bowie Knife" by Raymond Thorp in 1948. Darrell Garwood used it in a more scholarly book called "The Story of Kansas City" in 1948.

After which the phrase starts showing up in a smattering of historical journals in the late 1940s and early 1950s. Then it explodes following 1955, 90 years after Anderson's death, when Monaghan and Brownlee nationally mainstreamed the nickname that never was.