Origins of phrases

The phrase "rule of thumb" is said to have been derived from an old English law which stated that you couldn't beat your wife with anything wider than your thumb. It doesn’t because no such law existed. A more general law allowed the chastisement ‘in moderation’ of one’s wife but no ‘rule of thumb’ was ever mentioned. The phrase has been in circulation since at least 1692, when it appeared in print thus: "What he doth, he doth by rule of Thumb, and not by Art." (Sir W. Hope, Fencing-Master.) That makes it clear that the origin refers to one of the numerous ways that thumbs have been used to estimate things - judging the alignment or distance of an object by holding the thumb in one's eye-line, the temperature of brews of beer, measurement using the estimated inch from the joint to the nail, etc. It isn't clear which of these is the precise origin.

Smoked (red) herrings were once used to train hunting dogs by dragging the fish across the trail of the fox in an attempt to sidetrack the dogs. Poachers are also said to have used red herrings to sidetrack the hounds from the quarry which they then took.

John Dennis (1657-1734), a critic and unsuccessful playwright, devised a method of making the sound of thunder backstage. In 1704, Dennis's play Appius and Virginia was produced at the Drury Lane Theatre, London, using his new method. The play soon failed but shortly after the producers of a run of ‘The Scottish play ' used his thunder making idea. Dennis is alleged to have shouted “Damn then! They will not let my play run, but they steal my thunder.”

The two websites below are useful in tracing the alleged origins of some of the more interesting phrases in our language...

http://www.phrases.org.uk/meanings/index.html

http://www.businessballs.com/clichesorigins.htm