Plunkett-Ernle-Erle-Drax is the quadruple-barrelled

Double-barrelled name

In English speaking and some other Western countries, a double-barrelled name is a family name with two parts, which may or may not be joined with a hyphen and is also known as a hyphenated name. An example of a hyphenated double-barrelled surname is Bowes-Lyon; an example of an unhyphenated...

 surname of the descendants of Admiral The Honourable Sir Reginald Aylmer Ranfurly Plunkett-Ernle-Erle-Drax

Reginald Drax

Admiral The Hon. Sir Reginald Aylmer Ranfurly Plunkett-Ernle-Erle-Drax, KCB, DSO, JP, DL was a British admiral...

 (1880–1967), who was the younger son of the 17th Baron of Dunsany by his wife Ernle

Ernle

Ernle was the surname of an English gentry or landed family descended from the lords of the manor of Earnley in Sussex who derived their surname from the name of the place where their estates lay.-Onomastic:...

 Elizabeth Louisa Maria Grosvenor Ernle-Erle-Drax, née Ernle Elizabeth Louisa Jessica Burton (1855–1916). The surname of Plunkett-Ernle-Erle-Drax was assumed in lieu of Plunkett, his name from birth, by royal licence on 4 October 1916. Ernle is pronounced earnly. The current head of the family is the Westminster M.P., Richard Grosvenor Plunkett-Ernle-Erle-Drax, otherwise Richard Drax

Richard Drax

Richard Grosvenor Plunkett-Ernle-Erle-Drax , known as Richard Drax, is a former Army officer and journalist, now Conservative Party politician and Member of Parliament for South Dorset....

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See Burke's Peerage and Baronetage under the account of the Dunsany barony

Baron Dunsany

The title Baron of Dunsany or, more commonly, Lord Dunsany, is one of the oldest dignities in the Peerage of Ireland, one of just a handful of 13th to 15th century titles still extant, having had 20 holders to date...

for a complete listing of the Plunkett-Ernle-Erle-Drax family.