of a violin bow
(or bow of any other stringed instrument
) is often mistakenly referred to as the 'frog'.
According to The Oxford
Dictionary of Music, The Grove Concise Dictionary
, The New Grove Dictionary of Musical Instruments (vol 3, P-Z) and the Collins English Dictionary (3rd. ed.) the frog
is in fact the nut
in the heel
of the bow
which tightens the horsehair
of the bow.
The reason the heel of the bow is often referred to as the frog is because of the manner in which the musician holds the bow. S/he holds the bow near the frog, and the index and second and third fingers rest on the stick while the thumb presses on the underside of the frog.
(For more info on the violin refer to its node)