My father, the late Dr. Hans-Heinrich Bracker (1922-2007), did some family research told us the following about the origin of the surname Bracker:
The region of our Bracker ancestors lies in the middle of Schleswig-Holstein, especially the closer surrounding of the city of Neumünster (which can be seen by the frequency of that surname in this area). Often there are ponds at the edge of the villages and the trees on the shore of these ponds often had been fallen down due to stormy weather. The fallen trees led to a swampy character of the shore of these ponds. These ponds then were called (in lower German -> "Plattdeutsch") "Brook" / "Braak" (from the fact, that the trees had been broken down by the storms). So the etymology hints at the verb "brechen, brach, gebrochen" (in lower German "breken, breek, broken").
And the people who lived near one of these "Brooks" / "Braaks" were called "Bracker", pronounced with a long "a" (as in "bra").
This is what I remember; but my father was not a linguist and therefore I can't stand for the correctness of this etymology...
What can be said: many bearer of this surname emigrated from Schleswig-Holstein to the US; some also to Australia.
Hans-Juergen Bracker (*1961); I grew up in Schleswig-Holstein and live in the south of Germany, near Lake Constance.