What's the origin of the phrase 'beyond the pale'?
From World Wide Words:
Pale is an old name for a pointed piece of wood driven into the ground and — by an obvious extension — to a barrier made of such stakes, a palisade or fence. Pole is from the same source, as are impale, paling and palisade. This meaning has been around in English since the fourteenth century and by the end of that century pale had taken on various figurative senses — a defence, a safeguard, a barrier, an enclosure, or a limit beyond which it was not permissible to go. The idea of an enclosed area still exists in some English dialects.
The earliest figurative sense that’s linked to the idiom was of a sphere of activity or interest, a branch of study or a body of knowledge, which comes from the same idea of an enclosed or contained area; we use field in much the same way. This turned up first in 1483 in one of the earliest printed books in English, The Golden Legende, a translation by William Caxton of a French work.
The Phrase Finder adds that the first printed reference of the phrase "beyond the pale" (rather than just the word pale in its figurative sense) comes "from 1657 in John Harington's lyric poem The History of Polindor and Flostella."
In that work, the character Ortheris withdraws with his beloved to a country lodge for 'quiet, calm and ease', but later venture further - 'Both Dove-like roved forth beyond the pale to planted Myrtle-walk'. Such recklessness rarely meets with a good end in 17th century verse and before long they are attacked by armed men with 'many a dire killing thrust'. The message is clearly, 'if there is a pale, you should stay inside it', which conveys exactly the meaning of the phrase as it is used today.
When the Normans invaded Ireland in the twelfth century, they were not as successful as they hoped: the English possessions were gradually reduced to an area round Dublin. This was originally protected by a palisade (or Pale), and (in English eyes at least) Ireland was divided unto the civilised part within the Pale and the barbarian part "Beyond the Pale", which became a common phrase for the Elizabethans, if not earlier.
Pale in this idiom comes from Latin pālus 'stake'; it means a fencepost, and by ordinary extension it also means the fence itselt, and the area it contains or delimits.
So beyond the pale just means "outside the boundaries". Normally, of course, the "boundaries" are metaphors for human activities, rather than referring to a physically bounded location.
Etymonline.com says of pale (n.):
early 14c., "fence of pointed stakes," from L. palus "stake," related to pangere "to fix or fasten" (see pact). Figurative sense of "limit, boundary, restriction" is from c.1400. Barely surviving in beyond the pale and similar phrases. Meaning "the part of Ireland under English rule" is from 1540s.
I have always heard that it refers to the Pale of Settlement, but that name likewise came from pale meaning "stick".