Google is your friend:
http://dictionary.reference.com/browse/bucking wrote:Buck
[buhk]
noun
1.
lye used for washing clothes.
2.
clothes washed in lye.
verb (used with object)
3.
to wash or bleach (clothes) in lye.
Origin
1350-1400; Middle English bouken (v.); compare Middle Low German buken, büken to steep in lye, Middle High German būchen, bruchen
The same page also has
Buck
[buhk]
noun
1.
a sawhorse.
2.
Gymnastics. a cylindrical, leather-covered block mounted in a horizontal position on a single vertical post set in a steel frame, for use chiefly in vaulting.
3.
any of various heavy frames, racks, or jigs used to support materials or partially assembled items during manufacture, as in airplane assembly plants.
4.
Also called door buck. a doorframe of wood or metal set in a partition, especially one of light masonry, to support door hinges, hardware, finish work, etc.
verb (used with object)
5.
to split or saw (logs, felled trees, etc.).
Verb phrases
6.
buck in, Surveying, Optical Tooling. to set up an instrument in line with two marks.
Origin
1855-60; short for sawbuck
and from usage found on the web
The bucker used a bucking bar on the other side of the metal to smooth out the rivets.
Currently investigating the Hillmans of Sussex.