prison wardens called screws

[shivvy]

anyone know why?

[Clanad]

One site suggests the following: "...as underworld slang for a prison guard dating back to the mid-19th century, 'screw' was suggested by someone harsh and brutal, one who used thumbscrews on prisoners." From the "Encyclopedia of Word and Phrase Origins" by Robert Hendrickson (Facts on File, New York, 1997).

Screw as a term for a prison guard is based on the fact that screw was originally slang for "key." One of the most important functions of a prison guard, or turnkey, as he's often called, is to see that prisoners are locked up at the appropriate times -- and that involves turning the "screw." Interestingly enough, Henry Mencken reports in The American Language that in the 1920s deskmen and bellboys in hotels used screw as a slang term for room key. Another theory is that screw refers to the thumbscrews used by jailers in ancient times to torture prisoners into confessing.
From Morris Dictionary of Word and Phrase Origins, Second Edition (1988) by William and Mary Morris

Eric Partridge, in A Dictionary of Slang and Unconventional English, Fifth Edition (1961), also wrote:
*screw. A skelton key: c[ant]: 1975, Potter; slightly ob[solescent]. --2. ? hence, a turnkey or prison warder: 1821, Egan: c[ant] until ca. 1860, then low s[lang]....

[Quizmonster]

To give a somewhat more British slant to things...
Screw (in this particular slang sense) appeared in the mid 18th century to mean a false or skeleton key, as C says above. Perhaps because prison officers carry many keys around with them, the word became attached to them over the next fifty years or so. As a result, the earliest-recorded reference in print for screw = warder dates from 1812.
There is also a suggestion that the 'screw' was a name given to a mediaeval torture device, which was also used in prisons. Other than the 'thumb-screw' idea, it might even have been a sort of treadmill that prisoners had to 'work' on.
However, the 'key' connection is probably the most significant.

[Catso]

I've read it was because the warders could screw down the 'brakes' on the pointless 'hard labour' machines (EG the treadmill) so as to make the cons. work harder.

[Postdog]

The reason is that many years ago, prison was seen more as punishment than rehabilitation, and prisoners were given menial and sometimes pointless tasks to do.

One of these involved a mechanism they had to crank round x number of times - it was basically a handle turning a wheel which turned a counter. However it had a gearing system on which the prison officer could control - by turning a screw - the ease or difficulty of turning the handle. Consequently, they became known as "Screws".

[shivvy]

thanks to you all - very interesting indeed.

[Peter Pedant]

When I asked a prison warder whether a lady warder was a wardress

(after all a porter who is a nun is called a portress, not many of them about, I agree, but useful to have a definitie noun, should one ever meet one)

He said, they are all called prison officers, now.

PP