E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
When a gladiator was vanquished it rested with the spectators to decide whether he should be slain or not. If they wished him to live, they shut up their thumbs in their fists (polce compresso favor judicabatur); if to be slain, they turned out their thumbs. Adam, in his Roman Antiquities (p. 287), says, If they wished him to be saved, they pressed down their thumbs; if to be slain, they turned up [held out] their thumbs. (Pliny, xxviii. 2; Juvenal, iii. 36; Horace: 1 Epist., xviii. 66.)
It is not correct to say, if they wished the man to live they held their thumbs downwards; if to be slain, they held their thumbs upwards. Polce compressio means to hold their thumbs close.
Where, influenced by the rabbles bloody will,
With thumbs bent back, they popularly kill.
Dryden: Third Satire.
By the pricking of my thumbs, something wicked this way comes. Another proverb says, My little finger told me that. When your ears turn hot and red, it is to indicate that someone is speaking about you. When a sudden fit of shivering occurs, it is because someone is treading on the place which is to form your grave. When the eye itches, it indicates the visit of a friend. When the palm itches, it shows that a present will shortly be received. When the bones ache, it prognosticates a coming storm. Plautus says, Timeo quod rerum gesserim hic ita dorsus totus prurit. (Miles Gloriosus.) All these and many similar superstitions rest on the notion that coming events cast their shadows before, because our angel, ever watchful, forewarns us that we may be prepared. Sudden pains and prickings are the warnings of evil on the road; sudden glows and pleasurable sensations are the couriers to tell us of joy close at hand. These superstitions are relics of demonology and witchcraft.
In ancient Rome the augurs took special notice of the palpitation of the heart, the flickering of the eye and the pricking of the thumb. In regard to the last, if the pricking was on the left hand it was considered a very bad sign, indicating mischief at hand.
Do you bite your thumb at me? Do you mean to insult me? The way of expressing defiance and contempt was by snapping the finger or putting the thumb in the mouth. Both these acts are termed a fico, whence our expressions Not worth a fig, I dont care a fig for you. Decker, describing St. Pauls Walk, speaks of the biting of thumbs to beget quarrels: (See GLOVE.)
I see Contempt marching forth, giving mee the fico with his thombe in his mouth.Wits Miserie (1596).
I will bite my thumb at them; which is a disgrace to them, if they bear it.Shakespeare: Romeo and Juliet, i. 1.
Every honest miller has a thumb of gold. Even an honest miller grows rich with what he prigs. Thus Chaucer says of his miller
Wel cowde he stelë and tollen thries,
And yet he had a thomb of gold parde [was what is called an honest miller].
Canterbury Tales (Prologue, 565).
Rule of thumb. Rough measure Ladies often measure yard lengths by their thumb. Indeed the expression sixteen nails make a yard seems to point to the thumb-nail as a standard. Countrymen always measure by their thumb.
Tom Thumb. (See TOM.)
Under ones thumb. Under the influence or power of the person named.