E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Nephew to Montague, a testy, litigious gentleman, who would quarrel with a man that had a hair more or a hair less in his beard than he had. Mercutio says to him, Thou hast quarrelled with a man for coughing in the street, because he hath wakened thy dog that hath lain asleep in the sun. (Shakespeare: Romeo and Juliet, iii. 1.)