Q From Gill: Why do we say pulling your leg when we are teasing or having a joke with someone?
A Oh, dear, I wish we knew. People keep asking me this, but there’s very little evidence on which to base a sensible reply. It’s usually said that the term arose in the 1880s in Britain, since the first known reference appeared in W B Churchward’s Blackbirding in that year: “Then I shall be able to pull the leg of that chap Mike. He is always trying to do me”. But Jonathan Lighter, in the Random House Historical Dictionary of American Slang, has found an example from 1821, suggesting that it might both be much older and also known in America as well as Britain (although American sources usually suggest that it is indeed British in origin). There’s also a Scots version to draw the leg that might indicate its homeland is north of the border.
Some writers suggest it may have had something to do with tripping a person up as a joke, or figuratively tripping him by catching him out in some error to make him seem foolish. Others prefer to link it to street thieves, who might trip their mark up to make it easier to steal from him. But why either activity should be likened to pulling a person’s leg is unclear. It’s often ghoulishly said that it derives from the days of public hangings, in which friends of the condemned person would pull on his legs to speed the process of asphyxiation and so ensure a quicker death; but it’s hardly possible to equate that with a jape or deception.
None of these have any appeal except as stories. The truth is out there, but it’s keeping itself well hidden.