William T. Sherman And The American Term “Bum”- WAR SLANG
The term “bummers” refers to General Sherman’s foragers during the March To The Sea and the Carolinas Campaign and is possibly deriving from the German Bummler, meaning “idler” or “wastrel.” Many soldiers, who believed it struck terror in the hearts of Southern people, embraced the name.
Bummer. (1) A deserter. See also hospi- 
tal bummer. (2) An individual more in- 
terested in the spoils of war than in good 
conduct; a predatory soldier. (3) A ge- 
neric name for the destructive horde of 
deserters, stragglers, runaway slaves, and 
marauders who helped make life miser- 
able in the war-torn South. Bummers 
robbed, pillaged, and burned along with 
General Sherman and his army in Geor- 
gia. These men were known far and wide 
as Sherman's bummers. The term was not 
shortened to "bum" until after the war 
(c. 1870). It is almost certainly a mod- 
ification of the German Bummler 
("loafer").
On the road from Atlanta to the sea and then north, Sherman’s columns left their supply bases far behind, and their wagons could not carry provisions sufficient for all the Union troops. Sherman wanted to move fast and not be encumbered by supply trains or even worrying about protecting supply lines.  He therefore ordered the Yankee soldiers to live off the land.  Since it was Sherman’s intent, as we have already shown in his statements in the Official Records, “to make Georgia howl" to cause the citizens to suffer as much as possible he accomplished both objectives with use of the bummers.  The Yankees also intended to lay just as heavy a hand on South Carolina, because they considered a "hellhole of secession."
The bummer foraging parties became bands of marauders answering to no authority. One conscientious bummer wrote to his sister about the depredations inflicted on South Carolina: 
“How would you like it, what do you think, to have troops passing your house constantly … ransacking and plundering and carrying off everything that could be of any use to them? There is considerable excitement in foraging, but it is [a] disagreeable business in some respects to go into people’s houses and take their provisions and have the women begging and entreating you to leave a little when you are necessitated to take all. But I feel some degree of consolation in the knowledge I have that I never went beyond my duty to pillage.”
Source: http://www.npr.org/blogs/pictureshow/2011/06/28/137450464/3-d-motion-pictures-from-the-civil-war Source:http://archive.org/stream/War_Slang/War_Slang_djvu.txt Source:http://civilwar150th.blogdrive.com/

William T. Sherman And The American Term “Bum”- WAR SLANG

The term “bummers” refers to General Sherman’s foragers during the March To The Sea and the Carolinas Campaign and is possibly deriving from the German Bummler, meaning “idler” or “wastrel.” Many soldiers, who believed it struck terror in the hearts of Southern people, embraced the name.

Bummer. (1) A deserter. See also hospi- 
tal bummer. (2) An individual more in- 
terested in the spoils of war than in good 
conduct; a predatory soldier. (3) A ge- 
neric name for the destructive horde of 
deserters, stragglers, runaway slaves, and 
marauders who helped make life miser- 
able in the war-torn South. Bummers 
robbed, pillaged, and burned along with 
General Sherman and his army in Geor- 
gia. These men were known far and wide 
as Sherman's bummers. The term was not 
shortened to "bum" until after the war 
(c. 1870). It is almost certainly a mod- 
ification of the German Bummler 
("loafer").

On the road from Atlanta to the sea and then north, Sherman’s columns left their supply bases far behind, and their wagons could not carry provisions sufficient for all the Union troops. Sherman wanted to move fast and not be encumbered by supply trains or even worrying about protecting supply lines.  He therefore ordered the Yankee soldiers to live off the land.  Since it was Sherman’s intent, as we have already shown in his statements in the Official Records, “to make Georgia howl" to cause the citizens to suffer as much as possible he accomplished both objectives with use of the bummers.  The Yankees also intended to lay just as heavy a hand on South Carolina, because they considered a "hellhole of secession."

The bummer foraging parties became bands of marauders answering to no authority. One conscientious bummer wrote to his sister about the depredations inflicted on South Carolina: 

“How would you like it, what do you think, to have troops passing your house constantly … ransacking and plundering and carrying off everything that could be of any use to them? There is considerable excitement in foraging, but it is [a] disagreeable business in some respects to go into people’s houses and take their provisions and have the women begging and entreating you to leave a little when you are necessitated to take all. But I feel some degree of consolation in the knowledge I have that I never went beyond my duty to pillage.”

Source: http://www.npr.org/blogs/pictureshow/2011/06/28/137450464/3-d-motion-pictures-from-the-civil-war Source:http://archive.org/stream/War_Slang/War_Slang_djvu.txt Source:http://civilwar150th.blogdrive.com/