[wideawake]

Later this expression was generalized to identify ideas or activities that are out of bounds, as being "beyond the pale."

This is just incorrect.

The Russian word is cherta and is translated into English as "pale", but there were other pales of settlement in the English speaking world long before the Russian pale for Jews was established in 1785.

The area around Dublin settled by Englishmen was known as the Pale, the area around Calais was also known as the Pale and the area around Glasgow was known as the Scottish Pale.

The term "beyond the pale" was a colloquialism in England in the 1500s, more than two centuries before the Russian phenomenon.

[mc5cents]

True enough. This is what Robert Claiborne had to say about it in his book "Loose Cannons and Red Herrings":

Beyond the Pale: A "double" metaphor. The original pale was a stout stake with a pointed end; then, a fence (paling) made of such stakes. Whence the original metaphor: various "fenced" enclaves under English control---notably, Dublin and its environs ("the Pale"), which for many centuries was the only part of Ireland where England actually ruled.