BEAK (early forms beke and becke, from Fr. bec, late Lat. beccus, supposed to be a Gaulish word; the Celtic bec and beq, however, are taken from the English), the horny bill of a bird, and so used of the horny ends of the mandibles of the octopus, the duck-billed platypus and other animals; hence the rostrum (q.v.) or ornamented prow of ancient war vessels. The term is also applied, in classic architecture, to the pendent fillet on the edge of the corona of a cornice, which serves as a drip, and prevents the rain from flowing inwards.
The slang use of "beak" for a magistrate or justice of the peace has not been satisfactorily explained. The earlier meaning, which lasted down to the beginning of the 19th century, was "watchman" or "constable." According to Slang and its Analogues (J.S. Farmer and W.E. Henley, 1890), the first example of its later use is in the name of "the Blind Beak," which was given to Henry Fielding's half-brother, Sir John Fielding (about 1750). Thomas Harman, in his book on vagrants, Caveat or Warening for commen cursitors, Vulgarely called Vagabones, 1573, explains harmans beck as "counstable," harman being the word for the stocks. Attempts have been made to connect "beak" in this connexion with the Old English beag, a gold torque or collar, worn as a symbol of authority, but this could only be plausible on the assumption that "magistrate" was the earlier significance of the word.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)