Earl of Ossory is a subsidiary title

Subsidiary title

A subsidiary title is an hereditary title held by a royal or a noble but which is not regularly used to identify that person.For example, the Duke of Norfolk is also the Earl of Arundel, the Earl of Surrey, the Earl of Norfolk, the Baron Beaumont, the Baron Maltravers, the Baron FitzAlan, the Baron...

 held by the Earl of Ormond that was created in the Peerage of Ireland

Peerage of Ireland

The Peerage of Ireland is the term used for those titles of nobility created by the English and later British monarchs of Ireland in their capacity as Lord or King of Ireland. The creation of such titles came to an end in the 19th century. The ranks of the Irish peerage are Duke, Marquess, Earl,...

 in 1528.

In 1525, King Henry VIII of England

Henry VIII of England

Henry VIII was King of England from 21 April 1509 until his death. He was Lord, and later King, of Ireland, as well as continuing the nominal claim by the English monarchs to the Kingdom of France...

 became enamoured of Anne Boleyn

Anne Boleyn

Anne Boleyn ;c.1501/1507 – 19 May 1536) was Queen of England from 1533 to 1536 as the second wife of Henry VIII of England and Marquess of Pembroke in her own right. Henry's marriage to Anne, and her subsequent execution, made her a key figure in the political and religious upheaval that was the...

 and began pursuing her. As Henry's infatuation for Anne intensified, so did her father's titles. Henry arranged for the main claimant to the earldom of Ormond, Piers Butler to renounce all his claims to the titles in favour of Thomas Boleyn

Thomas Boleyn, 1st Earl of Wiltshire

Thomas Boleyn, 1st Earl of Wiltshire, KG was an English diplomat and politician in the Tudor era. He was born at the family home, Hever Castle, Kent, which had been purchased by his grandfather Geoffrey Boleyn, who was a wealthy mercer. He was buried at St. Peter's parish church in the village of...

. Butler was rewarded for his generosity by being created Earl of Ossory five days later.
In 1662, the eldest son of James Butler, 1st Duke of Ormonde

James Butler, 1st Duke of Ormonde

James Butler, 1st Duke of Ormonde PC was an Irish statesman and soldier. He was the second of the Kilcash branch of the family to inherit the earldom. He was the friend of Thomas Wentworth, 1st Earl of Strafford, who appointeed him commander of the Cavalier forces in Ireland. From 1641 to 1647, he...

 was called to the Irish House of Lords

Irish House of Lords

The Irish House of Lords was the upper house of the Parliament of Ireland that existed from mediaeval times until 1800. It was abolished along with the Irish House of Commons by the Act of Union.-Function:...

 on a writ of acceleration

Writ of acceleration

A writ in acceleration, commonly called a writ of acceleration, was a type of writ of summons to the British House of Lords that enabled the eldest son and heir apparent of a peer with multiple peerage titles to attend the British House of Lords or Irish House of Lords, using one of his father's...

 and became known as Thomas Butler, 6th Earl of Ossory

Thomas Butler, 6th Earl of Ossory

Vice-Admiral Thomas Butler, 6th Earl of Ossory, KG, PC, PC was the eldest son of the James Butler, 1st Duke of Ormonde and Lady Elizabeth Preston, and an Irish politician born at Kilkenny Castle.-Life and career:...

. His father held the title "5th Earl of Ossory" as one of his subsidiary titles, which made Thomas Butler the 6th Earl by courtesy. He predeceased his father and thus never became Earl of Ormonde in his own right.