English:

Quartered arms of w:Murrough O'Brien, 1st Earl of Thomond, 1st Baron Inchiquin. Quarterly of 4:

• 1&4: Gules, three lions passant guardant in pale per pale or and argent. A difference of the English royal arms of Plantagenet, granted by King Henry VIII at Greenwich in 1543, together with the Earldom of Thomond, to Murrough O'Brien, formerly Prince of Thomond;
• 2: Argent, three piles in point issuing from the chief gules, a difference of the Anglo-Norman family of de Bryan, Lord Justice of Ireland tempore King Edward VI (1547-1553);
• 3: Or, a pheon point down azure, arms of the English family of Sidney, w:Lord Deputy of Ireland, (1565–71 & 1575–78). See also, re: "The vexed question of the pheon" (per Cokayne, G. E. & Geoffrey H. White, eds. (1953). The Complete Peerage, or a history of the House of Lords and all its members from the earliest times, volume XII part 1: Skelmersdale to Towton. Vol. 12.1 (2nd ed.). London: The St. Catherine Press, Thomond, p.716, note (e)) Joseph Jackson Howard (Ed.), Miscellanea Genealogica et Heraldica, Vol.I, 3rd Series, London, 1896, pp.49-50, G.E.Cockayne, Bookplate of Charles O'Brien[1]

The O'Brien (Ó Briain) dynasty, kings of Munster, Ireland, was founded in the 10th century by w:Brian Boru who by conquest became High King of Ireland. Brian's descendants thus carried the name Ó Briain, continuing to rule the Kingdom of Munster until the 12th century when their territory had shrunk to the Principality of Thomond. The last Ó Briain to reign in Thomond was Murrough Ó Briain (d.1551) who surrendered his sovereignty to the new Kingdom of Ireland under the rule of King Henry VIII of England, being created instead (1543) w:Earl of Thomond and maintaining a role in governance. To show this resignation of the Gaelic Order and showing loyalty to the new king and government, the old heraldic arms (A dexter forearm grasping a sword in pale proper) (per The Chief Herald of Ireland’s office) were discarded (but retained as a crest) and King Henry VIII granted to Murrough his own personal arms of Plantagenet, differenced by tincture of the lions (party per pale or and argent) and by the absence of armed and langued azure (O'Brien, Donough, History of the O'Briens from Brian Boroimhe, AD. 1000 to AD. 1945, London, 1949, pp.50-54 & 198). "From an English point of view this was a great honor, but to the Ui Briain Clan, the Irish, and the Gaelic Order, it was surrender and defeat" (Garry Bryant / Garaidh Ó Briain, O'Brien Clan Heraldry, History of O’Brien Clan Heraldry, (Irish Armiger, 1992) [2])

Quarterings: The quarters are (2nd): Argent, three piles in point issuing from the chief gules and (3rd): Or, a pheon point down azure, both also adopted in 1543. Ivar O’Brien (1992) believes the three piles to be an earlier symbol of O’Brien of Arra in County Tipparary (a branch of the O’Brien Clan and described as being "a law unto themselves"). However strong circumstantial evidence suggests that they were a difference of the arms of the entirely unrelated Sir w:Francis Bryan (1490-1550) a courtier of King Henry VIII and Lord Justice of Ireland during the reign of his son King Edward VI, adopted to show loyalty to the English crown. Sir Francis Bryan was of the Anglo-Norman de Bryan family, from Devonshire in England and Pembrokeshire in Wales, founded by Guy de Bryan. The pheon was adopted to show loyalty to Sir w:Henry Sidney, w:Lord Deputy of Ireland, (1565–71 & 1575–78) whose family arms were identical: Or, a pheon point down azure (Ivar O’Brien, The O’Brien Arms: a Speculation of their Origin, The Royal O’Briens: a Tribute, 1992, p.61). See also: Garry Bryant / Garaidh Ó Briain, O'Brien Clan Heraldry, History of O’Brien Clan Heraldry, (Irish Armiger, 1992) [3]. See also: O’Brien Knot, a heraldic badge of the family, seen for example on a corbel next to the fireplace at Lemenah Castle in north-west County Clare.