The OED also has other (some very early) examples relating to literal or metaphorical 'pale' or 'pales', several specifically not in Ireland. It means fence.
b. A limit, a boundary; a restriction; a defence, a safeguard. Freq. in to break (also leap) the pale : to go beyond accepted bounds; to transgress. Now rare and literary.
"?a1525 (1475) Play Sacrament 207 (MED), Myt we yt gete onys within our pales, I trowe we shuld sone affter putt yt in a preve.
c1540 (▸?a1400) Gest Historiale Destr. Troy 13874 The buerne..Past ouer the pale and the pale ythes.
1612 T. Taylor Αρχὴν Ἁπάντων: Comm. Epist. Paul to Titus ii. 12 This is the pale, and preseruatiue of pietie.
1671 F. Philipps Regale Necessarium 515 Nothing within the pale or verge of Reason, or the fancy or imagination of any.
1713 C. Johnson Successful Pyrate i. i. 3 He has leapt the Pale of Custom, and is a Royal Out-law.
1751 Johnson Rambler No. 163. ⁋14 When the pale of ceremony is broken.
1790 G. Colman Battle of Hexham i. 21 Grim death, breaking the pale of time, shall stride the field with slaughterous step.
1817 Scott Poet. Wks. (1841) 661 Italian license loves to leap the pale, We Britons have the fear of shame before us, And, if not wise in mirth, at least must be decorous.
1869 W. J. Courthope Ludibria Lunae iv. 135 Now hath Science broke the pale. Your Gods are fled! Ye planets, hail!
1907 J. Davidson Triumph of Mammon i. i. 11, I broke the pale Of Christendom, displeased because no God Regarded me when..I sought A message from on high."
(Italics wouldn't work for some reason).
Now, I understand that people have told you about the Irish meaning of 'beyond the pale' for a long time, and you believed it. But the evidence for it is lacking. It really is.
You know on 'QI' when something that 'everybody knows' is shown not to be the case? This is like that.