"He's out there…totally beyond the pale of any acceptable human conduct." That's how the U.S. Army describes Marlon Brando's rogue colonel, Kurtz, in the movie Apocalypse Now. In his book The Audacity of Hope, President Obama described certain capital crimes as "beyond the pale"; this year, Paul Ryan has used the same phrase to condemn racist comments by Donald Trump. We may not know what "the pale" is, but boy oh boy can we ever tell when someone, or something, is beyond it. But I've got a surprise for you. You're probably beyond the pale right now—unless you're within a hour's drive of Dublin, Ireland. Here's why.

The other Norman Conquest didn't go so well.

By the 14th century, the Norman invasion of Ireland was struggling. Too many Normans had "gone native" like Colonel Kurtz and assimilated into Irish life. The remaining settlers had retreated to just four eastern counties: Louth, Meath, Dublin, and Kildare. These four "obedient shires" were the only part of Ireland still under the control of the English crown. The king's perimeter was marked with wooden fence posts pounded into the Irish turf. These were called "pales," from the Latin palus, meaning "stake."

A last "ditch" attempt to thwart cattle rustlers.

Over the following centuries, the English settlement fortified its boundaries by turning the fenceline into an impressive barrier: a ten-foot-deep ditch surrounded by eight-foot banks on each side and ringed by a thorny hedge. These ramparts were never meant to be an impregnable wall, but they did provide a daunting obstacle to raiders stealing across the borders for English cattle. Within the Pale ditch, settlers lived under the protection of the crown. But once you passed "the Pale," you were outside the authority and safety of English law, and subject to all the savageries of rural Ireland. "Beyond the pale" then became a colloquial phrase meaning "outside the limits of acceptable behavior or judgment."

Also beyond the pale: hipster haircuts.

The English made every attempt not to succumb to the culture "beyond the pale." Settlers were forbidden to intermarry with the Irish, and it was illegal to speak Gaelic. The woolen mantles worn by Irish peasants had to be exchanged for good English cloaks, and the "glib" was banned as well. Glibs were the fashionable Irish hairstyle of the day: hair cropped very short up top and in the back, with long, fringe-y bangs around the face. It's a 16th-century cut that wouldn't look out of place on a Park Slope barista today.

Head to County Meath for a Pale view of hills.

Under the Tudors, English influence and control gradually spread to all corners of the Emerald Isle, and "the Pale" as a political entity was no more. But sections of the ditch can still be seen cutting across the Irish countryside today, having become pasture borders centuries ago. One segment near the village of Syddan is intact for over a mile. You can ramble over the banks and see if you feel any different on either side of this medieval DMZ.

Explore the world's oddities every week with Ken Jennings, and check out his book Maphead for more geography trivia.