The 'Pale of Settlement' was a western border region of Imperial Russia in which permanent residence of Jews was allowed, extending from the "pale" or demarcation line, to live near the border with central Europe. The word "pale" derives ultimately from the Latin word "palus", meaning stake. ("Palisade" is derived from the same root.) From this came the figurative meaning of 'boundary', and the concept of a pale as an area within which local laws were valid. The phrase "beyond the pale" derives from this meaning of pale. Though comprising only 20% of the territory of European Russia, the Pale corresponded to historical borders of the Polish-Lithuanian Commonwealth and included much of present-day Lithuania, Belarus, Poland, Moldova, Ukraine, and parts of western Russia. Additionally, a number of cities within the pale were excluded from it.
http://www.globalsecurity.org/military/world/europe/de-aspirations-maps-1.htm
http://www.globalsecurity.org/military/world/europe/de-aspirations-maps-1.htm