“I will bite my thumb at them; which is a disgrace to them, if they bear it,” said Sampson of the house of Capulet to his fellow servant, Gregory, in Act I, scene 1, of Romeo and Juliet.
But a moment later, when it appeared that the servants of the house of Montague were not going to “bear it,” he amended the remark: “No, sir, I do not bite my thumb at you, sir, but I bite my thumb, sir.
That is, to bite one’s thumb was, and still is, an ordinary act, as ordinary and inoffensive as to bite one’s fingernail.
But “to bite one’s thumb at” a person was an insult of Shakespeare’s time not to be taken lightly, a sure cause for quarrel.
The gesture itself, as defined by Cotgrave (1611), meant, “to threaten or defie by putting the thumbe naile into the mouth, and with a ierke (from the upper teeth) make it to knack (click, snap).”
But the commentators of Shakespeare and others have not been able to determine the significance of the gesture, what it was intended to represent.
The conjecture is that it was equivalent to the indecent gesture of contempt, the thumb thrust between the fingers to represent a fig, but it is difficult to see what relationship there could have been between the two.