What is the origin of the term "bulldoze"?

Nobody really knows, which makes “bulldozer” one of those fascinating words whose meaning shifts depending on what people imagine its origin to be.

“Bulldozer” today most commonly refers to a kind of earthmoving tractor with a blade attached to the front. It can also mean a kind of bully or steamrolling force—a metaphorical meaning that, one would guess, came from the earthmover idea. In fact, the exact reverse is true. Bulldozer and bulldoze (the verb) are US slang that first turned up in the late 1800s to mean something intimidating or bullying, either literally or metaphorically. In at least some uses, large-caliber handguns were called “bulldozers.”

The word first popped up in print in newspapers, where it was frequently used along with a self-conscious explanation of its meaning. These etymologies generally claimed it came from “bull-dose,” a supposed slave plantation term for a whipping so severe it was a “dose” of punishment that would harm even a bull. This is fairly believable, especially presuming the influence of such terms as “bullwhip.” However, there are reasons to doubt it, especially since no one has found an independent prior usage of “bull-dose.” It is just as likely to be pop etymology that helped cement the intimidating tone of the word. It’s significant that at the time, “bull” could be used as a prefix in slang to denote something large. So a “bull-dose” could simply be a large dose of anything. But then, it’s also unclear how “dose” shifted into “doze”—if that’s indeed what happened. Early citations varying in their spellings, making it unclear which came first.

http://www.etymonline.com/index.php?term=bulldoze

bulldoze
1876, originally bulldose "a severe beating or lashing," lit. "a dose fit for a bull," a slang word referring to the beating of black voters (by either blacks or whites) in the 1876 U.S. presidential election. A bulldozer was a person who intimidates by violence until the meaning was extended to ground-clearing caterpillar tractor in 1930.

http://www.etymonline.com/index.php?search=bulldoze&searchmode=none

The origin of "bulldozer" turns out to have a surprising, and surprisingly unpleasant, origin. Today, of course, we know "bulldozers" as those big caterpillar-type tractors with broad blades mounted on the front, used to level earth or remove obstructions during construction.

The first "bulldozers," however, were not machines, but violent bullies. The root meaning of "to bulldoze" (or as it appeared originally around 1876, "to bull-dose") was to beat someone extremely brutally, inflicting the "dose" of flogging one would give a bull. Some of the earliest "bull-dozers" were racist thugs who terrorized African-Americans in the post-Civil War South, conducting a campaign of terror that included brutal beatings and murder. "Bulldozer" or "bull-doser" was also used to describe thugs in general, and by about 1881, the term was being used as slang for a very large pistol, as in one 1881 account: "A Californian bull-doser is a pistol which carries a bullet heavy enough to destroy human life with certainty."

Given the use of "to bulldoze" as a synonym for "to intimidate through overwhelming force" and "bulldozer" as a label for anything that "gets the job done," it's not surprising that "to bulldoze" soon took on the metaphorical meaning, still used today, of "push through" or "overwhelm." And when, in the early 20th century, a machine was invented that could uproot, overturn, level or just overwhelm anything in its path, it made perfect sense to call the contraption a "bulldozer."

http://www.word-detective.com/101800.html