cross the mouth of a river or harbour as a means of defence. Possibly
from the metaphor of a breaking boom, and the accompanying rush and
roar, or from the rush of rising waters (mingled with the onomatopoeic
use), "boom" began in America to be used of a sudden "spurt" or access
of industrial activity, as in the phrase "a boom in cotton." Hence the
verb "to boom," meaning to advertise or push into public favour.

BOOMERANG, a missile weapon of the Australian aborigines and other
peoples. The word is taken from the native name used by a single tribe
in New South Wales, and was mentioned in 1827 by Captain King as "the
Port Jackson term" (_Nav. Surv. Coasts Austral._ i. 355) It has been
erroneously connected with the _womera_ or spear-thrower, and equally
erroneously regarded as onomatopoeic--for it does not "boom" but
whistles in the air. Two main types may be distinguished: (a) the return
boomerang; (b) the non-return or war boomerang. Both types are found in
most parts of Australia; the return form was, according to General
Pitt-Rivers, used in ancient Egypt; and a weapon which has a close
resemblance to the boomerang survives to the present day in North-East
Africa, whence it has spread in allied forms made of metal (throwing
knives). Among the Dravidians of South India is found a boomerang-shaped
instrument which can be made to return. It is, however, still uncertain
whether the so-called boomerangs of Egypt and India have any real
resemblance to the Australian return boomerang. The Hopis (Moquis) of
Arizona use a non-return form. The general form of both weapons is the
same. They are sickle-shaped, and made of wood (in India of ivory or
steel), so modelled that the thickness is about 1/6th of the breadth,
which again is 1/12th of the length, the last varying from 6 in. to 3 or
4 ft. The return boomerang, which may have two straight arms at an angle
of from 70 deg. to 120 deg., but in Australia is always curved at an
angle of 90 deg. or more, is usually 2 to 3 ft. in length and weighs
some 8 oz.; the arms have a skew, being twisted 2 deg. or 3 deg. from
the plane running through the centre of the weapon, so that B and D
(fig. 1) are above it, A and E below it; the ends AB and DE are also to
some extent raised above the plane of the weapon at C; the cross section
is asymmetrical, the upper side in the figure being convex, the lower
flat or nearly so; this must be thrown with the right hand. The
non-return boomera