"By hook or by crook" is an English phrase meaning "by any means necessary", suggesting that one need not be concerned with morality or other considerations when accomplishing some goal.
The origin of the phrase is obscure, with multiple different explanations and no evidence to support any particular one over the others. For example, a commonly repeated suggestion is that it comes from Hook Head

Hook Head

Hook Head is a headland in County Wexford, Ireland located on the east side of the estuary of the three sisters rivers . It is part of the Hook peninsula and is adjacent to the historic townland of Loftus Hall...

 in Wexford

Wexford

Wexford is the county town of County Wexford, Ireland. It is situated near the southeastern corner of Ireland, close to Rosslare Europort. The town is connected to Dublin via the M11/N11 National Primary Route, and the national rail network...

, Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 and the nearby village of Crook, in Waterford

Waterford

Waterford is a city in the South-East Region of Ireland. It is the oldest city in the country and fifth largest by population. Waterford City Council is the local government authority for the city and its immediate hinterland...

, Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

. Another is that it comes from the customs which regulated which firewood local people could take

Estovers

In English law, estovers is wood that a tenant is allowed to take, for life or a period of years, from the land he holds for the repair of his house, the implements of husbandry, hedges and fences, and for firewood....

 from common land

Common land

Common land is land owned collectively or by one person, but over which other people have certain traditional rights, such as to allow their livestock to graze upon it, to collect firewood, or to cut turf for fuel...

; they were allowed to take any branches that they could reach with a billhook

Billhook

The billhook is a traditional cutting tool known and used throughout the world, and very common in the wine-growing countries of Europe, used widely in agriculture and forestry The billhook (also bill hook – although this more usually refers to either a metal or plastic hook used to hold bills,...

 or a shepherd

Shepherd

A shepherd is a person who tends, feeds or guards flocks of sheep.- Origins :Shepherding is one of the oldest occupations, beginning some 6,000 years ago in Asia Minor. Sheep were kept for their milk, meat and especially their wool...

's crook. The first recorded use of the phrase is in the Middle English

Middle English

Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

 text Controversial Tracts by John Wyclif in 1380.

In the British TV show The Prisoner

The Prisoner

The Prisoner is a 17-episode British television series first broadcast in the UK from 29 September 1967 to 1 February 1968. Starring and co-created by Patrick McGoohan, it combined spy fiction with elements of science fiction, allegory and psychological drama.The series follows a British former...

, the beginning of each episode

Opening and closing sequences of The Prisoner

The opening and closing sequences of TV series The Prisoner are considered iconic, "one of the great set-ups of genre drama."-The Prisoner overview:...

 contains the phrase, with Number Two

Number Two (The Prisoner)

Number Two was the title of the chief administrator of The Village in the 1967-68 British television series The Prisoner. More than 17 different actors appeared as holders of the office during the 17-episode series .The first...

 stating that The Village

The Village (The Prisoner)

The Village is the fictional setting of the 1960s UK television series The Prisoner where the main character, Number Six, is held with other former spies and operatives...

 authorities will gain information from the protagonist Number Six

Number Six (The Prisoner)

Number Six is the central fictional character in the 1960s television series The Prisoner, played by Patrick McGoohan. In the AMC remake, the character is played by Jim Caviezel, renamed "Six"....

"by hook or by crook."