An arrow. The feathers under the beak of a hawk were called barb feathers (beard feathers). The point of an arrow has two iron “feathers,” which stick out so as to hinder the extraction of the arrow. (Latin, barba, a beard.)
N.B. —The barb is not the feather on the upper part of the shaft, but the hooked iron point or head.
A Barbary steed, noted for docility, speed, endurance, and spirit. (See Barbed Steeds.)
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894